xhtml transitional vs strict?

Question

iframes are not supported in xhtml strict. However, in my application I am using php recaptcha which requires the use of iframes. What are the downsides of just switching to xhtml transitional (if any)?

Answer 1

Has hobbs said, there is no practical downside. However, theoretically the strict DTD is more "future-proof".

Here's a link to a quick fix in PHP that will make recaptcha valid XHTML 1.0 Strict:

http://www.boriel.com/2009/07/29/xhtml-strict-valid-recaptcha/

Answer 2

Nothing, really. In practical terms, when it comes to browser compatibility, functionality, and tool/generator friendliness, XHTML 1.0 Transitional (following the "HTML compatibility" guidelines and served as text/html) is your best bet.

Answer 3

Here you have an small comparison that can help you regarding each type of document.

But in "practical" terms if you want to keep your site using strict, why just add the iframe. the only issue with this is that page wont be correctly validated

Answer 4

At the time HTML4 was written, it was thought that iframes would be phased out in future.

However, that was a long time ago, and it looks like that is no longer the case. Thus, you could say that the 'strict' subset is no longer as accurate a representation of the future of HTML/XHTML as it once was.

Use transitional if there's a reason you need some of its features, but have a good understanding about which features are 'deprecated' and in general avoid them where there's a better alternative.

Note that browser support for transitional features implemented today probably isn't going to disappear in my lifetime. Backward compatibility has proven a tough nut to crack on the web.