TEK PEEK

Mod_pagespeed automatically implements a number of performance-optimization techniques that can help improve the loading times of the sites that implement it.

It is employed by google to increase page speed.

now google has launched Mod_pagespeed 1.2

through which progressive jepg and smart catching is available 

caching-related optimization in mod_pagespeed 1.2 is support DNS prefetching

this is a remarkable achievement by google