Does not Validate

Do you mean the default theme? A link would help show what the problem is.

Also, CSS is not checked in the XHTML validator. Try https://jigsaw.w3.org/css-validator/check/referer for checking your CSS.

i bet a dollar to a doughnut the validations (if on the default theme) fault is the fault of a article/post with an un- alt’ed image..

but there is a css validation engine on w3c I use all the time.