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Firefox 3 has been out for two weeks now, so get with the program: It's time to hack it. The newest version of Mozilla's browser has plenty of new features, including the site identification button, the Bookmarks Library and what has become known as the "Awesome Bar" -- and I'll show you how to hack them all.

You can also force the browser to use Gmail for mailto: links, discover a hidden "Easter egg" and more. So fire up your browser and get ready to teach it some new tricks.

A note before we begin: One of the best ways to hack Firefox 3 is via about:config, which lets you change a wide variety of Firefox settings and preferences. Many of the hacks in this story make use of this nifty and practical utility.

To use about:config, you'll always repeat a few basic steps:

1. In the address bar, type about:config and press Enter.

2. A message will appear reading "This might void your warranty!" Ignore that nonsensical warning and click "I'll be careful, I promise!"

3. In the filter box, type the name of the setting you want to adjust. You'll see that entry appear in the area below. (If the name of the setting is very long, typing the first part of it will generate a list; you can then pick the setting you want.)

4. Make changes to the setting as instructed.

1. Klaatu Barada Nikto!

You may not know it, but Firefox has a mascot -- a robot that you can find in a hidden Easter egg in Firefox 3. In the address bar, type about:robots and you'll see the cheerful metal guy. The robot-related quotes displayed are from books and movies in which robots play a significant role, such as Blade Runner and The Hitchhiker's Guide to the Galaxy .

If you look at the title for the page, you'll find what at first glance may seem to be gibberish: Gort! Klaatu barada nikto! In fact, that's the phrase used by Helen Benson in the science fiction classic The Day the Earth Stood Still , ordering the robot Gort not to destroy the Earth.

2. Tell Firefox 3 to Have Yahoo Mail Handle mailto: Links

Until Firefox 3, if you used a Web-based e-mail account such as Yahoo Mail or Gmail, you were left out in the cold when you clicked a mailto: link. Mailto: links automatically begin an e-mail message to a specific sender, using your default e-mail handler. But with previous versions of Firefox, those links worked only with client-based e-mail software, and not with any Web-based e-mail programs.

With Firefox 3, that changes. The browser includes built-in integration with Yahoo Mail -- if you know where to look. And although it doesn't have the same integration with Gmail, there's a way to hack it to make it do so.

1. Select Tools -- Options and click the Applications icon at the top of the page.

2. Click mailto, and select Use Yahoo! Mail.

3. Click OK.

From now on, when you click a mailto: link, you'll be sent to your Yahoo! Mail account and a new e-mail will be created, to be sent to where the mailto: link directed it. (If you're not already logged into Yahoo Mail, you'll have to type in your username and password first.)

3. Tell Firefox 3 to Have Gmail Handle mailto: Links

Gmail, surprisingly, doesn't show up in the Firefox list of mailto: handlers. But you can add it. Just follow these steps:

1. In the address bar, type about:config and press Enter. Ignore the warranty warning.

2. In the filter box, type gecko.handlerservice.

3. From the entries that appear, double-click gecko.handlerServiceAllowRegisterFromDifferentHost. This will change its value from false to true.

4. In the address bar, copy this code, exactly as you see it, then press Enter:

javascript:window.navigator.registerProtocolHandler("mailto",
"https://mail.google.com/mail/?extsrc=mailto&url=%s","GMail")

5. Below the address bar, you'll get a message asking if you want to add Gmail as the application for mailto: links. Click the Add Application button.

6. Next time you click a mailto: link, a screen will appear that lets you choose an appropriate application. Select Gmail, check the box next to "Remember my choice for mailto: links," then click OK.

From now on, Gmail will handle the links. As with Yahoo Mail, if you're not currently logged in, you'll first have to type in your e-mail and password, and then Gmail will create the e-mail.