Go to the Google toolbar for firefox page at Google, and click the download link. A "Terms and conditions agreement" page is returned by Google. Read it carefully, and if you agree, press the "Agree and Install" button.

You probably get the following warning by Firefox at the top of the page just after you click the button: "To protect your computer, Firefox prevented this site (toolbar.google.com) from installing software on your computer.". Just click on the Edit Options button to the right of this warning to open the "Allowed Sites - Software Installation" dialog.

Make very sure that the address matches toolbar.google.com before you press the Allow button. Be very careful with adding sites to this list, there are sites that try to make you install software you really don't want to have running on your computer.

After toolbar.google.com has been added to the list, close the "Allowed Sites" dialog by pressing the Close button. Next, press the "Agree and Install" button on the "Terms and conditions" page again. The "Software Installation" dialog should appear. Again, veryify what you're going to install: google-toolbar.xpi from http://toolbar.google.com/. Then press the Install Now button.

The "Extensions" dialog should appear, and download (about 358 KB) the Google Toolbar extension. The actual installation of the extension takes place when you restart Firefox. So close all open Firefox windows, and start the browser again.

After starting Firefox the Google Toolbar opens a post-install dialog, which lets you select the search site and make Google the default search search engine in Firefox. It also adds toolbar.google.com to the list of allowed software providers. You have already done this manually in order to download this extension.

Like I wrote at the beginning of the article, the feature of the Google Toolbar I use a lot is the PageRank reporting feature. Since Google only can report the PageRank if it knows the address of the site you are visiting, the extension has to send the address of the site to Google. If you consider this information too sensitive to share with Google, make sure you disable the PageRank feature.