you seem to have more of a hand for XHTML 1.0 Transitional , that looks more like the coding style you should use.
you have some errors there, but not as many serious ones.
most of the errors are easy to fix ones, like
should be
etc.
will take you 10 min to have the site validate as XHTML 1.0 Transitional, which is your best bet, your missing a few div closes.
also add alt="whatever" to a few images that don’t have alt characters. but for the most part you will easily get it to validate with the above.
gl