latest firefox version for fc4

[list user]

Hi all!

I had Firefox-1.0.4 on my fc4 installation, and just did a "yum update 
firefox".  Upon success I now have 1.0.8.

Visiting mozilla.org I see that the current version of firefox is 1.5.0 
which fixes certain security issues.

I further note there are version numbers and release numbers.

Could somebody shed some light on the relationship between fedora 
versions vis a vis mozilla versions/releases?

Don't like running things that may have security issues :(

Thank you,
Mike Wright