Alexpizzoferro, Thanks for the good reference and explanation.
Sash, You can use these scripts for XHTML for PC browsing, but remember that (for now atleast) most mobile phone browsers cannot process Javascript or VBScript.
Using XHTML, your some mobile phones can display things like radio buttons, text entry fields, submit buttons, etc.
Check the "Nokia_GSM_WAP_Phone_WML_and_XHTML_Elements" document for the supported XHTML tags for each type of phone. It can be downloaded from www.Forum.Nokia.com in the "Browsing/WAP" >> "Documents" section.