Why??

ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6.16/

Firefox 3.6.16 had some serious security issues that were corrected in Firefox 3.6.17. See the items corrected in Firefox 3.6.17 here: https://www.mozilla.org/security/known-vulnerabilities/firefox36.html

For those that really need an ancient version of Firefox releases or with the latest of Firefox 3. Mac OS X 10.4 users can't upgrade to 4.0.1 and Mac OS X 10.5 users need the Intel chip.

By the way there will be a Firefox 3.6.18 security update release when Firefox 5.0 is also released on June 21 at earliest.

new version of firefox all very well but sync doesn't work/load.....

@mingo, it's probably worth starting a new question about Sync. That will capture your system information and bring more attention to your question.

https://support.mozilla.com/en-US/questions/new