Do modern browsers care about the DOCTYPE?

Question

If you use deprecated attributes or tags

, , or etc. in XHTML 1.0 St

Answer 1

Browsers do care about the DOCTYPE - otherwise there wouldn't be any point in having it!

You are right in saying that many browsers interpret old/deprecated commands in the correct way, but this is largely a matter of backwards compatibility. There is such a huge amount of content on the web that it is next to impossible to keep everything up-to-date and standards-complient. The web browsers continue to support these outdated pages because if they didn't, much of the content on the web would look slightly off. Most users don't know the difference between HTML4 and 5, so the blame could fall on the browser, which could be devastating - especially if a page looks bad on Firefox and nice on IE!

The DOCTYPE is mainly used in validation and to determine whether a browser runs in this "quirks mode" (where many of these older rules still work) or "standards mode" . Many professional web designers use the W3C validation tools to make sure their web pages are valid HTML, and the tools provided by their website look at the DOCTYPE to choose the correct set of rules with which to validate. Furthermore, XHTML strict does not allow empty tags or other blatant syntactic errors.

Hope this helps!