I have noticed that there are many shops that are not using Magento’s default feature to merge JavaScript files. At the time prior to Magento 1.4, JavaScript merging was included.

All you need to do is:

 

1) Go to admin section
2) Go to System->Configuration->ADVANCED (Developer)
3) Set “Merge JavaScript Files” to Yes (“No” is default)
4) What left is to Flush Javascript/CSS Cache at Cache management admin interface.

 

That’s it!, All Javascripts of the page will be merged into one, and reduces the page requests.
Take a look at this images to compare before and after:

BEFORE:

AFTER:

 

 

You Can also use third party plugins like Fooman,GTspeed. To speed up your Webstore You can get the plugins from MagentoConnect.

What these Plugins will Actually do?

They'll minify your css by eliminating whitespaces, comments, and merges them all.

Enables Caching, Which Prevents unnecessary requests.

Merges the Javascripts, and reduces the Page loading time.

This is a simple idea, can help your Webstore to load faster.

Hope this one helps you.