This is a template for slides for TPAC 2023.

To write slides, look at the slides in this template or read the user manual at the end.

To start the slide show, turn on JavaScript and press ‘A’. Return to the index with ‘A’ or ‘Esc’. On a touch screen, use a 3-finger touch. Double click to open a specific slide. In slide mode, press ‘?’ (question mark) to get a list of commands.

If it doesn't work: Slide mode requires a recent browser with JavaScript. If you are using the ‘NoScript’ add-on (Firefox or the Tor Browser), or changed the ‘site settings’ (Chrome, Vivaldi, Opera, Brave and some other browsers), or the ‘permissions for this site’ (Edge), you may have to explicitly allow JavaScript on these slides. Internet Explorer is not supported.

Leaving presentation mode.



★ W3C TPAC 2023, Seville, 11–15 September ★


This is an H3

  1. Potatoes
  2. Onions and olives

Another H3

Some elements

Words can be given a strong emphasis, which makes them appear in bold

The normal emphasis has a highlighter effect.

Code looks like this: if (a) return b;

This link goes to slide 2

This is an example of a note, in a smaller font

Incremental display (1/3)

Unfold (default style)

  • This item is shown right away

Fade in (class=emerge)

  • This item is shown right away

Incremental display (2/3)


Fade in + red items
(class="emerge strong")

Incremental display (3/3)

Quick + greeked
(class="quick greeked")

Fade in + red + dim (class= "emerge strong dim")

Elements updated in-place

Combining class=incremental with class=in-place yields elements that are displayed one by one, with each one replacing the previous. Example:

  1. First element
  2. The second replaces the first
    until it itself is replaced
  3. The third replaces the second.

(class=overlay is an alias for class=incremental.)

An image on the side

[Picture of a stylized tree with colorful, square leaves]

It seems the famous ‘lorem ipsum’ is based on a text by Cicero, but with the lines mixed up. On a Cicero by the text, it seems the ‘ipsum lorem’ is famous based with lines but mixed up.

An image on the side

[Picture of a stylized tree with colorful, square

And again, with class slide side right.

It seems the famous ‘lorem ipsum’ is based on a text by Cicero, but with the lines mixed up. On a Cicero by the text, it seems the ‘ipsum lorem’ is famous based with lines but mixed up.

A ‘bleeding’ image

[Top view of four pairs of hand holding each other crosswise]

Adding class cover to the image makes it stretch to the edges of the slide.

Hint: Add class=clear on the slide to omit the banner and slide number.

A ‘bleeding’ image

[Top view of four pairs of hand holding each other crosswise]

And also on the right side…

A big image on the side

[Picture of a stylized tree with colorful, square leaves]

It seems the famous ‘lorem ipsum’ is based on a text by Cicero, but with the lines mixed up. On a Cicero by the text, it seems the ‘ipsum lorem’ is famous based with lines but mixed up.

A big image on the side

[Picture of a stylized tree with colorful, square leaves]

And again, with class ‘slide side right big’.

On a Cicero by the text, it seems the ‘ipsum lorem’ is famous based with lines but mixed up.

A big, ‘bleeding’ image

[Top view of four pairs of hand holding each other crosswise]

It seems the famous ‘lorem ipsum’ is based on a text by Cicero, but with the lines mixed up. On a Cicero by the text, it seems the ‘ipsum lorem’ is famous based with lines but mixed up.

A big, ‘bleeding’ image

[Top view of four pairs of hand holding each other crosswise]

And on the right side…

A figure

pie chart

The description of the pie chart, here as a table:

Name Percentage
Andy 16%
Chloe 21%
Daniel 13%
Grace 20%
Sophia 30%

In columns


Children of an element with a class of columns are distributed over two columns


This is the second child, which goes into the right column


And this is the third one. Left column again.


place t l
place t
place t r
Here is something for the left side, with class place l
class place puts an element centered in a 3×3 grid
place r
place b l
place b
combine place with top (or t), right (or r), bottom (or b) and left (or l)

Numbered lines of code

Lines in a PRE can be numbered
  * Give the PRE a class of "numbered"
  * Works for up to 20 lines
                       (depending on font size)

Striped tables

row 1has no background
row 2has a light gray background
row 3has no background
row 4has a light gray background

Image overlay: cover

Image: Statue of Gutenberg

Careful, some images make the text hard to read!

Image overlay: fit

Image: Statue of Gutenberg

Careful, some images make the text hard to read!

White text

[photo with a beach, cliffs, buildings, dark clouds and a surfer]

(Photo ‘Surfer and the stormy sea’ by Xavier Nohet)

Shout and grow!


Takahashi method!

Shout & Grow:


Grow: Don't use this too often!

Slide transitions

The style sheet predefines several transitions: fade-in, slide-in, move-left, etc.

A transition can be set globally, applying to all slides; or locally, applying only to the transition between this slide and the next.

Convert to PDF

Print in portrait mode to get:

  • multiple slides per page
  • notes between the slides

📃︎ Try it! [W3C team only]

A4 or Letter

Print in landscape mode to get:

  • one slide = one page
  • no notes

📃︎ Try it! [W3C team only]

PDF slides


  1. Making slides is easy
  2. Questions?

User manual

Setting up your slides

This is a template for slides for TPAC 2023. It uses either the Shower script (version 3.2) or the b6+ script for the presentation and has a style sheet based on the TPAC 2023 visual style. (To enable Shower, uncomment the script tag in the HTML source.)

All slides for TPAC 2023 have to be online. If you cannot put them online yourself, you can download a zip (see below) with everything needed to develop slides offline and ask Coralie for help uploading the slides once they are ready.

Developing slides online (W3C team)

Writing slides online (with JigEdit, WebDav or CVS) is only available to the W3C team. Make a directory under Copy the Overview.html from into your directory and edit the content, or just use it as an example.

Developing slides offline

If you develop your slides offline (or plan to present them without a network), then download this zip file. Unpacking it creates the following directories and files:

Make a directory for your own slides under TPAC-2023. You can copy the Overview.html file there as a starting point, or just use it as an example. If you make any images, put them in that directory as well.

If you are able to upload your slides, put your directory with all that it contains under There is no need to upload the Templates directory. It is is already there.

Writing slides


Each slide is a section element with a class of slide:

<section class="slide">
  ... slide content here...

Inside the slides, use normal HTML elements (p, ul, em, etc.).

Speaker notes or comments

You can add additional text, such as speaker notes or explanations, between the slides. They will be visible in index mode but not in slide mode. Use elements with a class of comment:

<section class="comment">
  ... text here...

Slide numbers

If a slide should not have a slide number and an image banner, add the class clear:

<section class="slide clear">
  ... slide content here...

On title slides and final slides (see below), this only removes the number, not the banner.

Adding the class clear on the body element omits the slide number and the side banner from all slides.

Title slides (cover slides)

For cover slides (the title slide or separator slides between parts of a presentation), add a class cover. You can combine cover and clear. E.g.:

<section class="slide cover clear">
  <h1>My presentations<h1>
  <address>Peter W. Slidemaker</address>

Final slide

The class final is meant for a last slide, e.g., for conclusions or thanks (but it may be used elsewhere, too):

<section class="slide final clear">

Illustrations on the left or right

Slides with narrower text and an illustration on the left or right can be made by adding the class side to the slide. Inside the slide there should be exactly one element that also has a class of side (an image or some other element). Two sizes are possible: normal (about 1/3 of the slide) and big (about 2/3 of the slide).

To put an image on the left:

<section class="slide side">
  <img src="..." alt="..." class="side">
  ... slide content here...

To put the image on the right instead, add class right (which may be abbreviated to r):

<section class="slide side r">
  <img src="..." alt="..." class="side">
  ... slide content here...

Add class big to the slide for a bigger image. To put the image on the left:

<section class="slide side big">
  <img src="..." alt="..." class="side">
  ... slide content here...

And on the right:

<section class="slide side r big">
  <img src="..." alt="..." class="side">
  ... slide content here...

The image can be stretched to the edges of the slide by adding a class cover. The image is not deformed. It is scaled to be big enough to cover the image area and then either the sides are cropped (if it is too wide) or the top and bottom*.

<section class="slide side big">
  <img src="..." alt="..." class="side cover">
  ... slide content here...

How big should images be? It actually depends on the size of the screen on which the slide is displayed. An image with too few pixels becomes blurry, but a big image takes long to load. It is actually possible to make images in several sizes and let the browser download the best one for the current screen, but that is too long to explain here. (Check out the picture element of HTML.) As a compromise, let's assume the slides are displayed full-screen on an HD projector (or an HDTV).

An HD projector has 1920×1080 pixels. A side image on such a screen occupies a space of 982 pixels high and 463 pixels wide (or 986 pixels wide with class big). So that leads to the following cases:

  1. A normal side image (without big and without cover): Make an image that is 463 pixels wide and no more than 982 pixels high; or an image that is 982 pixels high and no more than 463 pixels wide.
  2. A big side image (without cover): Make an image that is 986 pixels wide and no more than 982 pixels high; or an image that is 982 pixels high and no more than 986 pixels wide.
  3. A normal side image with cover (without big): Make an image that is exactly 463×982 pixels.
  4. A big side image with cover: Make an image that is exactly 986×982 pixels.

But note that for many non-critical images, especially photos, it doesn't matter if they are a bit blurry. You can often make images half as wide and half as high without ill effects.

*) Note for advanced users: It is possible to indicate which sides should be cropped: add an attribute like style="object-position: 20% 60%" to indicate that, of the amount to be cropped from the sides, 20% should be cropped on the left and the remaining 80% on the right; and of the amount to be cropped from the top and bottom, 60% should come from the top and the remaining 40% from the bottom. Thus, e.g., ‘0% 100%’ says never to crop anything from the left (0%) if the image is too wide, and only to crop from the top (100%) if the image is too tall. (The default corresponds to ‘50% 50%’, i.e., crop equal amounts from both sides.)


When information is in the form of an image (a diagram, a chart, a screenshot, etc.), put it inside a figure element. Add a figcaption if needed.

<figure><img src="..." alt="..."><figure>

If the image is not accessible, use a details element instead and add a description, like this:

 <summary><img src="..." alt="..."></summary>
 ... the same data as in the image, but as text...

The description becomes visible when the user clicks on the image. (The slide above shows an image of a pie chart that is described by a table with the same data.)

Automatic slide shows

This feature is only available with the Shower script, not with b6+.

Slides can be made to advance automatically after a given time, by setting a data-timing attribute on them with a value of MM:SS (minutes and seconds). E.g.,

<section class="slide" data-timing="1:03">

This slide will remain on screen no longer than 1 minute and 3 seconds, after which the next slide will be shown.

Progress bar

If you want a progress bar during the slide presentation, add an empty div with a class of progress. It can be put before the first slide or after the last, but there should be at most one such element in the file:

<div class="progress"></div>

The progress bar will show as a thin red line along the top of the slides. Its length increases from zero on the first slide to 100% on the last.

B6+ also sets a custom style variable --progress with a value between 0 and 1 on the body. This may be useful if you write your own style rules for a progress indicator.

Incremental display

To progressively reveal elements on a slide, put a class of next on all elements that should not be visible right away. They will become visible one by one as you press the space bar or an arrow key. E.g.:

  <li>This item is visible when the slide appears
  <li class="next">This item is not immediately visible
  <li class="next">This is the third item to appear
<p class="next">This is the last element to appear

By default, each new element appears with a short animation as if it unfolds from left to right. Two alternative animations are available: emerge makes the elements fade in and quick omits the animation. The class can be set on each incremental element:

<li class="next emerge">...

or on an ancestor, e.g.:

<ul class="emerge">
  <li class="next">...

Three optional modifiers change how elements look before, after or while they are the currently active element: Strong makes the currently active element red. Greeked replaces the elements that are not yet visible by a gray bar. (Useful to show how many elements are still invisible.) And dim grays out the elements that are no longer the active element.

Like the animation, these modifiers can be set on the incremental element itself or on an ancestor. The modifiers can also be combined, e.g.:

<ul class="emerge strong dim">
  <li class="next">...

Two columns

To put elements side by side in two columns, make an element (a div, ul or any other element) with class columns. The first child of that element will be put in the left column, the second child in the right column. If there are more children, the third will be in the left column again, the fourth in the right, etc.

<ul class="columns">
  <li>First goes on the left</li>
  <li>Second goes on the right</li>

Small text

Less important text can be shown in a smaller font by giving it a class of note:

<p class="note">Note that this is harder to read</p>

Extra big text: shout

To make text extra big, give it a class of shout, e.g.:

<p class=shout>Hurray!

(Sometimes this is referred to as the ‘Takahashi method’: Instead of sentences or graphics, a slide only contains one or two keywords. The narrative comes from the speaker.)

Animated text: grow

To draw extra attention to some text or an image, it can be animated. Adding a class of grow to it will make it appear slowly. It will start small and one second after the slide appears it will begin to grow and reach its normal size three seconds later.

<p class=grow>See?

Automatic line numbering

Pre-formatted text (in a pre) can be given line numbers by adding the class numbered:

<pre class="numbered">

No more than 20 lines will be numbered. (In the normal font size, a slide fits 13 lines.)

3×3 Grid

It is possible to treat the slide as a 3×3 grid and put elements in the four corners, in the middle of each edge, or in the center of the slide. This is done by giving the elements a class of place. On its own, place puts the element in the center. By adding classes top, right, bottom and left the element can be placed in one of the eight other positions.

<div class="place">Put this in the center</div>
<div class="place bottom">Put this bottom center</div>
<div class="place top right">In the top right</div>

The direction classes can also be abbreviated to t, r, b and l.

Image overlays (background images)

To put an image behind the text of a slide, use an img with a class of cover:

<img class="cover" src="..." alt="...">

The image will be stretched to fill the whole of the text area. If the image doesn't fit exactly (wrong aspect ratio), the image will be cropped.

With a class of fit instead of cover, the image will be scaled but without cropping. Instead there may be white bands on the sides or above/below the image, if it doesn't fit exactly.

<img class="fit" src="..." alt="...">

This works both for normal slides and title slides (slides with a class of cover). The logo on the right is not obscured by the image.

As explained above (see ‘Illustrations on the left or right’), the optimal size of an image depends on the screen the slide is shown on. But as a compromise, you can assume the common case of an HD projector, i.e., 1920×1080 pixels. The optimal image for cover is an image of exactly that size. The optimal image for fit is an image that is either 1920 pixels wide and at most 1080 pixels high, or an image that is exactly 1080 pixels high and at most 1920 pixels wide.

It is advisable to add a class of white or black to a slide with an image overlay. See the next section.

Forcing white text or black text

The colors of the slides depend on whether ‘dark mode’ is in effect in the operating system: black text on a white background if dark mode is off and white on black if it is on. But when text is overlaid on an image, it may be better to force the text to always be white (if the image is dark) or black (on a lighter image). You do that by setting a class on the slide: white (for white-on-black) or black (for white-on-black). E.g.:

<section class="slide white">

Other colors (titles, list bullets, links, etc.) also become fixed on such slides.

Slide transitions

By default, each slide just replaces the previous one, but there are several predefined slide transitions. You can set a transition on the body element to apply it to all slides:

<body class="shower fade-in">

Or you can set it on individual slides, to apply only to the transition between that slide and the next. (I.e., it doesn't determine how the slide appears, but how it disappears.)

<section class="slide wipe-left">

You can set both a global transition and local ones. The global transition applies to slides that do not have an explicit transition set locally.

The new slide appears faint at first and gets more opaque until it completely obscures the previous slide.
The new slide moves in from the left, while the previous slide moves back to the left.
The current slide moves out to the left, revealing the new slide.
The new slides move in from the right while the old slide moves out to the left.
The old slide moves up, revealing the new slide.
The old slide moves up and the new slide moves in from the bottom.
A 3D effect: the bottom of the old slide is lifted up and the slide is turned over to reveal the new slide on its back side.
Another 3D effect, but in this case the right side of the slide is lifted up and the slide is flipped over to the left, revealing the new slide on the back side.
A small circle appears in the middle of the old slide that reveals the new slide. The circle grows until it covers the whole slide.
The new slide moves in from the right, until it covers the old slide.
A zigzag pattern moves in from the right. To the left is the old slide, to the right the new one.
A zigzag pattern moves in from the left. To the left is the new slide, to the right the old one.
The new slide moves in from the top left and covers the old slide.

Watermark overlay

You can make a ‘watermark’, a text or an image that is overlaid on every slide, by making an element with a class of watermark. It can be placed before or after the slides.

<p class=watermark><strong>DRAFT!</strong>

By default, the watermark is slightly rotated and placed in the center of each slide. Any text will be red.


When you present while using a screen reader, you cannot use the screen reader's usual keystrokes to navigate, only the keystrokes defined by the b6+ script. However, the screen reader will speak each slide as soon as it appears. The script creates an element with attributes role=region and aria-live=assertive for that purpose.

When you leave presentation mode, the screen reader will say ‘stopped’. To make it say something else (e.g., because you want a different language than English), create an element with role=region and aria-live=assertive yourself and put the text to speak in it. E.g.:

<div role="region" aria-live="assertive">

Exporting to PDF

The slides can be exported to PDF (or printed) in two ways: multiple slides per page with comments interleaved, or one slide per page without any comments. The latter may be useful to create a PDF suitable for presenting, when it is not possible to use an HTML browser.

When printing in portrait mode, the output will contain as many slides per page as will fit and the comments are printed between the slides. This corresponds to viewing the slides in index mode.
When the output is in landscape mode, each page consists of one slide, without page margins, and without the comments between the slides.

Note: In landscape mode, the style sheet tries to set the size of the output page to exactly the size of a slide, but not all user agents that produce PDF respect that. (And, obviously, a printer is limited to the available paper.) There may be some black margin to the right and below each slide. Prince does respect the size. W3C team can also use the ",pdfui" tool online.


Mouse gestures and keystrokes

To present the slides, load them into a browser that supports JavaScript and CSS and then press the A key or double-click on a slide or touch the screen with three fingers (on certain devices).

If you are using Shower instead of b6+, press Shift+F5 (Command+Enter on Mac) or click on a slide.

Navigate though the slides by clicking the left mouse button, pressing the spacebar, the arrow keys or Page-up/Page-Down. The Home and End keys jump to the first, resp. last slide. F1 toggles full screen mode. The ? (question mark) key shows a list of available commands.

To exit the presentation, press the Esc key.

For more keys, see the documentation for keys & gestures in b6+ or keyboard shortcuts in Shower.

Using two screens or two windows

B6+ (but not Shower) can open a second window to preview the current and next slides and show notes. If you have two screens that can show different content (e.g., your computer's screen and a projector), you can thus present the slides on one screen, and see the current and next slides, and any notes, on the other.

Open the second window by pressing the ‘2’ key. (If it creates a tab, drag it out of the tab bar to make it a window.) Every time you go to a new slide, this second window will scroll to show the same slide (with incremental elements already expanded). If you make the window large enough, you can also see the next slide, and any notes you put under the slides.

Note: If you reload the slides, the script forgets that the second window exists and thus will not synchronize it. Just press ‘2’ again and it will reconnect to the second window.

Clocks to show remaining time

When using a second screen, it is possible to show clocks on that screen with the remaining time, the time used so far, and the real (wall clock) time. (The clocks are normally only shown on the second screen, but they can be included in slides or overlaid on slides, with suitable CSS rules.)

By default, the clocks will count down from 30 minutes and show a warning 5 minutes before the end. (In the style used for this document, the clock turns from green to orange.) You can set different times with the following classes:


To set the duration to, e.g., 45 minutes, add duration=45 to the class attribute of the body. Example:

<body class="duration=45">

To set the warning to, e.g., one minute, put this in the class of the body:

<body class="warn=1">

B6+ has two kinds of clocks built-in, but also provides primitive elements with which to build your own clock.

To get one of the built-in clocks, make an empty element with a class of either fullclock or clock. The former will display the real (wall clock) time, the number of minutes so far, the number of minutes left, a small ‘pie-chart’ showing the proportion of time used, and four buttons: subtract one minute, add one minute, pause the clock, and reset the clock. The simple clock will display the pie chart and the four buttons (somewhat smaller) and the remaining minutes.

When you make your own clock, you can make use of the following classes and attributes:

hours-real, minutes-real, seconds-real

B6+ will fill all elements with a class of hours-real with the current hour (wall-clock time) and keep them up to date. The hour will always be two digits and use a 24-hour clock: 00 to 23.

Similarly, all elements with a class of minutes-real or seconds-real will contain the current minutes or seconds, respectively, also always as two digits, 00 to 59. E.g.:

<b class=hours-real>00</b>:<b class=minutes-real>00</b>
hours-used, minutes-used, seconds-used

Elements with these classes will contain the time since the slides where loaded (or since the clock was reset, see timereset below). E.g.:

<b class=minutes-used>00</b>'<b class=seconds-used>00</b>"
hours-remaining, minutes-remaining, seconds-remaining

Ditto, but for the time still remaining. If the used time exceeds the duration, these times will be shown as 00.

timeinc, timedec

An element with a class of timinc will act as q button that increments the duration, and thus the remaining time, by one minute. timedec decrements the duration by one minute. E.g.:

<button class=timeinc>+1 min</button>
<button class=timedec>−1 min</button>

An element with this class acts as a toggle to pause & resume the clocks. When the clocks are paused, the used time does not progress and the remaining time does not diminish. (The real time clocks continue, of course.) When the element is clicked again, the clocks resume. E.g.:

<button class=timepause>pause</button>

An element with this class acts as a button to restart the clocks, i.e., to set the used time to zero. Example:

<button class=timereset>reset</button>

In addition to setting the time in elements with the classes mentioned above, b6+ also updates the style property, the class and a data- attribute on the body. This is useful for style rules to change the styles of elements based on the progress of the slide show. In particular, b6+ sets the following:

This custom style property on the body will be set to a value between 0.0 and 1.0, representing what fraction of the duration has been used.
This attribute on body will be set to the percentage of the duration already used. This will be a whole number with two digits between 00 and 99, or 100.
When the remaining time is less than the warn time, b6+ will add this class to the classes on body.

Starting in slide mode

Add ‘?full’ at the end of the URL (but before any fragment ID) to open the slides in slide mode instead of index mode.

To open in slide mode at a specific slide, add ‘?full’ and the ID or the number of the slide, e.g., Overview.html?full#place or Overview.html?full#25.

Hiding the mouse pointer

When you don't want the mouse pointer to remain on the screen in slide mode, add the class hidemouse on the body element. If the mouse does not move for 5 seconds, the pointer is made invisible. It comes back as soon as the mouse is moved.

<body class="hidemouse">

You can also set a different timeout in seconds. E.g, to set a short timeout of 1.5 seconds:

<body class="hidemouse=1.5">

Ignore mouse clicks

Normally, a mouse click anywhere on a slide (other than on a hyperlink or form element) has the effect of advancing to the next slide or incremental element. If you don't want that, add the class noclick on the body element.

<body class="noclick">

The complete list of key strokes and gestures is in the b6+ documentation, which also shows what else b6+ can do.

Embedding slides in other documents

You can embed a single slide in another document with the help of an <object> or <iframe> element. To avoid that a keypress or click accidentally changes the slide, you can disable navigation and index mode: add ‘?full&static’ at the end of the URL, followed by ‘#’ and the ID or number of the desired slide. E.g.:

<object data="Overview.html?full&static#18">...</object>


<iframe src="Overview.html?full&static#18"></iframe>

Adding ‘?static’ on its own to the URL is also possible: It shows all slides in index mode and disables switching to slide mode.

Speaking guidelines

The W3C's global audience is thankful to speakers for following the essential guidelines:

These guidelines are crucial because they transcend language barriers, foster comprehension, provide people the time to get acquainted with the subject by reading the slides in advance, and in some cases translate them into other languages, in other cases share and discuss them with colleagues before traveling to the meeting. You can read them in full in the Speaker Resources W3C public wiki.

*) Please, ask Coralie for help, including putting your slides on the Web.