Hi

If you want, I am sure I could find the download for Firefox 3.6, but I would strongly recommend against using it.

In the years since it was released, Firefox has had many security and functional improvements that make the latest product much better and safer for both you and your computer to use.

I would always recommend you use the latest version of Firefox.

To add onto what Seburo says:

Firefox 3.6 came out in 2010. It is VERY old in terms of software and especially web browsers. Firefox is currently on version 36.0.4 and version 37 comes out next week. You should ALWAYS be running the latest version of a web browser. Don't believe me? If you are using 3.6, you are vulnerable to most of the bugs at https://www.mozilla.org/en-US/security/known-vulnerabilities/firefox/, and your browser can't use all the new features http://en.wikipedia.org/wiki/History_of_Firefox#Version_4.0 from version 4 down (there are lots). You are stuck in technology 5 years old and can't use all the modern awesomeness.

Honestly, if your website building tool only supports Firefox 3.6, you should consider finding a new tool. There are lots of modern web technologies (like HTML5, CSS3, etc.) that that tool is probably forcing you to miss out on.

If you really need to use that tool, can't upgrade, and firefox 3.6 is the only version that works (I'd try using it with modern Firefox, it might work) then use the portable version of Firefox 3.6 and use regular Firefox for all your regular surfing. (http://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox,%20Portable%20Ed./Mozilla%20Firefox,%20Portable%20Edition%203.6.28/)