I don't know
XHTML is just basically reformed html, nothing really different about it other than W3C classifies it differently and it has a couple more restrictions than normal HTML does.
XHTML has no proprietary code such as
Code:
<center></center> <marquee></marquee>
and a few other codes. XHTML suggests that you instead use
Code:
<div style="align:center;"></div>
something like that, or use CSS instead of using "proprietary code"
XHTML also requires you to end some of your codes
like this:
Code:
<img src="http://forums.x10hosting.com/programming-help/xxx" />
not this:
[code]
<img src="xxx">
XHTML also requires every tag and attribute be lowercase
Not acceptable:
Acceptable
XHTML also has some strict standards on spacing, like
Acceptable
Not acceptable
Code:
< img src = " xxx " />
And those are the main ones I can think of.