lucy24 - 9:08 pm on Aug 5, 2011 (gmt 0)
Who is your target audience? What types of user agent (computer or mobile device) are they likely to be using? What type of connection are they likely to be on?
CSS is generally cumulative. That is, if it's in CSS1 it will probably be in newer versions. HTML4 vs XHTML and HTML4 vs HTML5 isn't.
"Strict" is silly. It just leads to double the verbiage as you have to say <blahblah style = "attribute: moreblahblah"> instead of <blahblah attribute = "moreblahblah"> when you hit something that can't go in the CSS or that only occurs once.