MacinSpot

FireFox is a much better browser for Macs because it comes with support for more webpages. It has all the features that Safari has plus a few extras. To install FireFox click here and click the green “Download Firefox - Free” button on the left side of the page. Mozilla.com automatically detects whether you have 10.4 or 10.5 so do not worry about which version of Mac OS X you have.
Once clicked it will start to download automatically.

It will download a DMG file to where ever you have specified in Safari’s preferences. My downloads are set to be downloaded to the “Downloads” folder in my Home folder so I don’t clutter my desktop.

Once downloaded it will open the DMG file and pop up a window that looks like this:

Drag the large FireFox logo on the left by clicking and holding down the left mouse button, then move it to the Applications folder on the right.
After you have done this you want to eject the drive that was mounted. On your desktop you will see:

Drag this to the trash to eject it. FireFox is now installed on your system. You can go back and delete the dmg file that was originally downloaded too as you do not need this anymore.
This installation method is a standard for installing most applications on your Mac. Other applications such as Skype and Yahoo Messenger use this same method. Just find the download page, download the dmg file, if it doesn’t open automatically as it usually doesn’t when downloading with FireFox, find the file on your system(usually on the desktop or in the downloads folder of the user’s home folder) and double-click it.

I hope this helps!