HTML and CSS Reference
The W3C validator supports the following character encodings: UTF-8, UTF-16, ISO-8859-1, ISO-8859-2,
ISO-8859-3, ISO-8859-4, ISO-8859-5, ISO-8859-6-i, ISO-8859-7, ISO-8859-8, ISO-8859-8-i, ISO-8859-9, ISO-8859-10,
ISO-8859-11, ISO-8859-13, ISO-8859-14, ISO-8859-15, ISO-8859-16, US-ASCII, EUC-JP, Shift_JIS, ISO-2022-jp, EUC-kr,
gb2312, gb18030, big5, Big5-HKSCS, tis-620, koi8-r, koi8-u, ISO-ir-111, Macintosh, Windows-1250, Windows-1251,
Windows-1252, Windows-1253, Windows-1254, Windows-1255, Windows-1256, and Windows-1257.
Both document type and character encoding are detected automatically and used for validation accordingly.
If detection is not possible, the validator assumes the document type and/or character encoding; however, the
results might be unreliable. Properly served standard-compliant web documents always provide both data; thus,
the validator performs validation accurately. The validator can also be forced manually to use certain document
type and/or character encoding; however, this feature should not be used in general cases. It should be considered a
fallback mechanism rather than an overriding feature.
If there are errors in the markup, they are clearly indicated by the red stripe and the number of errors (Figure 14-1 ).
Even the favicon of the page becomes a red square.
Figure 14-1. The red stripe and the number of errors and warnings clearly show that the markup is invalid
The consecutive errors and potential errors are listed under the summary sequentially by default, in other words,
in the order of occurrence (location in the markup). This behavior can be overridden to group error messages by error
type. Since many errors can cause further ones (such as a missing closing tag), sequential checking is appropriate in
■ Because of the high potential of correlation between markup errors, it might be convenient to correct some
errors only (especially if the document is full of errors) and then revalidate the document. the number of errors might
decrease exponentially. revalidation is also useful for testing implementations of special or new markup specifications as
a direct input.