Let me start by saying that HTML5 and CSS3 are two different things. Secondly HTML5 is still just HTML and CSS3 is still just CSS. I’ve been noticing that people are confusing these two specifications with each other and making it more complicated then it is.
Remember HTML5 is HTML, the new doctype; <!DOCTYPE html> is backwards compatible. If you like me always coded using the XHTML way, it is still valid. There aren’t any issues with closing your tags, personally I find it neater and easier to keep the code error free.
But besides all technicality, it will continue to be HTML5 pure for marketing purposes, that’s why the W3C has commissioned a logo to represent HTML5.
Once you have created your barebone form it is time to style it with CSS. Add some gradients to the fields, create a nice image free button and use some nice font.
The HTML5 code
The CSS3 code