Example for Checkpoint
9.3 - For scripts, specify logical event handlers rather than device-dependent event handlers.

An event-handler invokes a script when a certain event occurs (e.g, the mouse moves, a key is pressed, the document is loaded, etc.). In HTML 4.0, event handlers are attached to elements via event handler attributes (the attributes beginning with "on", as in "onkeyup").

What happens when an event occurs depends on the script the page author has created. Some produce purely decorative effects such as highlighting an image or changing the color of an element's text. Others produce much more substantial effects, such as carrying out a calculation, providing important information to the user, or submitting a form. For scripts that do more than just change the presentation of an element, content developers should do the following:

Use application-level event triggers rather than user interaction-level triggers. In HTML 4.0, application-level event attributes are "onfocus", "onblur" (the opposite of "onfocus"), and "onselect". Note that these attributes are designed to be device-independent, but are implemented as keyboard specific events in current browsers.

Otherwise, if you must use device-dependent attributes, provide redundant input mechanisms (i.e., specify two handlers for the same element):

• Use "onmousedown" with "onkeydown".
• Use "onmouseup" with "onkeyup"
• Use "onclick" with "onkeypress"
• Note that there is no keyboard equivalent to double-clicking ("ondblclick") in HTML 4.0.

To Checkpoints for Guideline 9.