1. Choose between the two libraries to achieve best performance.
2. Option to exclude single or multiple css / JS files. This is quite helpful, as not all the files like to be compressed or optimized.
3. Option to check server cache or client cache.
4. Option to choose optimization, Combine CSS files or use both options together.
2. DO NOT use it for livesite unless you have tested them carefully.
3. If your website are not rendered correctly, try to disable JS merge, or put important js file on the exception list
Check the Backend Settings Preview :
Watch the live comparison
With the help of Yslow , a firefox extension, lets see how the speed & the http request are optimized.
Below is the comparison of how JA Compress boost the speed for JA Purity II & JA Teline III templates.
JA Compress Plugin : JA Compress Plugin for Joomla 1.5