jQuery

jQuery simplifies the following

1. HTML document traversing
2. Event handling
3. Animating
4. Ajax interactions

Advantages:

1. Lightweight Footprint(zipped format)
2. CSS3 Compliant(Supports CSS3)
3. Cross-browser(Supports many browsers)

Demo:

http://www.w3schools.com/jquery/tryit.asp?filename=tryjquery_hide