HTML and CSS Reference
and CSS, it is important to find validation tools to verify that your markup is correct,
especially when conforming to the DOM and W3C standards. There are a number of free
tools on the Web to help you make sure your markup is valid.
The W3C validation tool is shown in Figure 1.17. This tool allows you to validate by
URI, file upload, or by direct input. This validator checks the markup validity of Web
documents in HTML, XHTML, SMIL, MathML, and so on, but to evaluate specific con-
tent such as RSS/Atom feeds or CSS stylesheets, MobileOK content, or to find broken
links, there are other validators and tools available.
Figure 1.17 The W3C markup validation of an HTML page.