1) Forget about XHTML, it's dead, use the HTML5 doctype it works well with even older browsers
2) From building a semantic form you gain exactly: nothing. Search engines won't give you traffic because you got a semantic form, and browsers won't render them better.
4) You should NOT CARE about whether the device is a handled or a tablet, you SHOULD care about it's screen size, aspect ratio, whether it has a mouse etc.
1) Forget about XHTML, it's dead, use the HTML5 doctype it works well with even older browsers
2) From building a semantic form you gain exactly: nothing. Search engines won't give you traffic because you got a semantic form, and browsers won't render them better.
3) SPECIFICITY will help you produce huge CSS, that will make your life a living hell. http://www.stubbornella.org/content/2010/07/01/top-5-mistake...
4) You should NOT CARE about whether the device is a handled or a tablet, you SHOULD care about it's screen size, aspect ratio, whether it has a mouse etc.