HTML 5 Form Validations

HTML 5 has introduced Javascript plug-ins to achieve something similar effect.

But these code will only work in Safari 5, Chrome 6, Opera 9, Firefox 4 Beta and the iPhone/iPad. Also each browser has a slightly different default behaviour.

The "required " attribute

The simplest change you can make to your forms is to mark a text input field as 'required':

Different versions of HTML

HTML is an evolving language, and each new version is given a number. The first definitive version was HTML 2.0 -- this had most of the elements we know and love, but was missing some of the Netscape/Microsoft extensions, and did not support tables, or ALIGN attributes.

HTML 3 (late 1995) was an ambitious effort on the part of Dave Raggett to upgrade the features and utility of HTML. However, it was never completed or implemented, although many features were integrated in the next "official" version of HTML, known as HTML 3.2.