Yslow

Yslow >>> Why my website is slow ??

Yslow is an addon for mozilla integratted with firebug (Another addon from
mozilla).

Yslow checks the web page and tells us what are the slow factors in the current
webpage and it put grade for a particular web page

High speed webpages get grade A. (Google is an example for A grade website)
and the grade varies to B, C , D etc depends on the speed of the webpage

Yslow catagarises the slow factors into 13 parts.

http://developer.yahoo.com/yslow/

Use this link for more details.

https://addons.mozilla.org/en-US/firefox/addon/5369

Install yslow from above url.