Except when you use browser specific stuff like -moz-blablabla or -webkit-blablabla, it doesn’t validate
bump ! I have another question. Can we choose “yes” in “valid html” when submitting a theme even if the CSS doesn’t valid (because of CSS3 ) ? Or is it HTML only ?
It might be the live preview only, validation is checked during the review but I don’t know…
and what about multiple accounts ?
your hosting company may provide stats
It’s not a must, it’s totally up to you and there are no absolute requirements about plugins, sliders, etc.
It seems like you have been successfull, congratulations !