Tools - Refactoring HTML: Improving the Design of Existing Web Applications - page 28

Validators
There really are standards for HTML, even if nobody follows them. One way to find out whether a site follows
HTML standards is to run a page through a validation service. The results can be enlightening. They will provide
you with specific details to fix, as well as a good idea of how much work you have ahead of you.
The W3C Markup Validation Service
For public pages, the validator of choice is the W3C's Markup Validation Service, at http://validator.w3.org/ .
Simply enter the URL of the page you wish to check, and see what it tells you. For example, Figure 2.1 shows
the result of validating my blog against this service.
Figure 2.1. The W3C Markup Validation Service
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