Want to tell your users to update their browser version?

Link here.

Polyfills for incapable browsers ( Webshims Lib )

Best thing about this plugin is that it only downloads the features that are not supported by a browser. That means, the more features supported by a browser, more lightweight the plugin gets.
Link here

Bits and pieces about HTML 5 FORMS !

Link here.
A look into the browser support for different new html5 forms by wufoo.

Link here.
Modernizr helps to check which css3 features are available in the current User Agent easily. 
Even, a specialized and minified js can be generated here which checks for only those features that we want.
This helps a lot in front end designing front ends on different browsers.

Link here.
Webforms2 is a script to implement cross browser html 5 forms. Even for old browsers like IE6-7, Safari 3, Mozilla 1 etc.

Link here.
To dive into html 5 input types ! and form validation types ! I love the way, the author has explained small simple changes that can be done for html5 upgradation. 

Link here and here.
Pretty interesting html5 form validation techniques. Also features a script that runs fallback functions for browsers not supporting html5. But, the posts are 2 year old. So a lot of changes would have taken place since then. Still, is a good read.

Link here.
A javascript library for non supporting html5 browsers at github basically for forms.


Link here.
To check which input attributes are supported by which browsers on desktops.
&
Link here.
To check which input attributes are supported by which browsers on mobile.

Check usability

Link here


To check if a particular feature in css, jss, html5 etc works in a particular browser version or not.