Hello All,

We have 3 websites needed to be changed into css design.Is there any website that provide free css templates design and possible to modify with the source files? Please help us.

There probably are some css 'templates' someplace maybe google for them?
...but that takes all the fun out of it. You can also get ideas from other sites' pages.
If you see something you like: view the page source using your browser's view > souce.
Most of the time css information will be found in other files that 'go with' the page.
To get them too, 'save' the page 'complete' and looking at the files saved.
To learn how to make use of what you might find you can visit these fine tutorials:
w3schools.com/default.asp or
tizag.com/