Intended audience: HTML/XHTML and CSS content authors. This material is applicable whether you create documents in an editor, or via scripting.
This tutorial gathers together and organizes pointers to articles that, taken together, help you understand how to handle the essential aspects of authoring (X)HTML and CSS related to characters and character encodings.
This section is for people in a hurry who just want to know the key recommendations from the tutorial. If you don't understand something, or if you want more detail, read the rest of the tutorial.
Save your pages as UTF-8, whenever you can.
Always declare the encoding of your document. Use the HTTP header if you can. Always use an in-document declaration too. This table tells you how, depending on what format you are authoring. Use encoding names from the IANA registry.
Use the @charset rule for external style sheets (but not CSS in your HTML page) if you have non-ASCII content, such as font names, ids or class names, etc.
Try to avoid using the byte-order mark in UTF-8, and ensure that your HTML code is saved in Unicode normalization form C (NFC).
Avoid using character escapes, except for invisible or ambiguous characters. And don't use Unicode control characters when you can use markup instead.
The articles pointed to describe the latest thinking with respect to the HTML5 specification. It is important to note, however, that the HTML5 specification is still not stable, so you should approach that information with care.
If you are a newcomer to this topic, there are certain foundational concepts you need to understand if you are to follow various parts of the tutorial. If you are familiar with these concepts, you can skip to the next section.
Content is composed of a sequence of characters. Characters represent letters of the alphabet, punctuation, etc. But content is stored in a computer as a sequence of bytes, which are numeric values. Sometimes more than one byte is used to represent a single character. Like codes used in espionage, the way that the sequence of bytes is converted to characters depends on what key was used to encode the text. In this context, that key is called a character encoding.
There are many character encodings to choose from. This part of the tutorial offers simple advice on which character encoding to use for your content, and how to apply it.
Choosing & applying a character encoding includes the following:
You should always specify the encoding used for an HTML or XML page. If you don't, you risk that characters in your content are incorrectly interpreted. This is not just an issue of human readability, increasingly machines need to understand your data too. You should also check that you are not specifying different encodings in different places.
Declaring character encodings in HTML will provide you with quick recommendations for those who just want to be told what to do, and more detailed information for those who need it.
Declaring character encodings in CSS provides information for CSS.
The byte-order mark, or BOM, is something you will come across when using a Unicode-based character encoding, such as UTF-8 and UTF-16. In some cases you will need to remove the BOM, in others you need to ensure that it is there.
The byte-order mark (BOM) in HTML covers:
Normalization is something you need to be aware of if you are authoring HTML pages with CSS style sheets in UTF-8 (or any other Unicode encoding), particularly if you are dealing with text in a script that uses accents or other diacritics.
Normalization in HTML and CSS covers:
You can use a character escape to represent any character from the Unicode character set in HTML, XML or CSS using only ASCII characters.
Using character escapes in markup and CSS provides information on the following:
Finally, there are a range of control-like Unicode characters, some of which fulfill the same role as markup. The question is, which should you use, and which should you avoid?
Characters or markup? covers: