[TYPO3-english] question about XHTML compliant

[tom]

Hi,

If you want to create XHTML compliant websites you can also do that with
TYPO3...(MTB1)

My question is: what does "XHTML compliant websites" mean? most sites are
Html Transitional, right? what kind sites we should make as XHTML compliant
websites?
I googled online, but still did not understand. Can give me some ideas
about this? Thanks.

Tom