my website (here) is almost done, and I currently have a Page speed score of 86, which is not too bad

I'd like to know if it's easy to get a faster site, but I dont understand Page Speed recommandations :
- Defer parsing of Javascript : 488.5KiB of JavaScript...
- Leverage browser caching...but cache is already enabled in J! config....as seen below
http://screencast.com/t/cMlC9IhldrT
Yahoo Slow adds:
- Combine background images with CSS sprites.
- Configure Entity Tags

Is it easy to follow one or several of these recommandations, and How to do that please ? thx, Adrien