How to permanently disable speed dial in Firefox
Firefox 13's speed dial feature displays your most frequently visited sites as thumbnails. If you're not a fan of the new feature, you can turn it off permanently.
In the latest release of Firefox, new tab pages display your nine most frequently visited Web pages in an easy-to-see thumbnail layout. You can customize the sites that are displayed and even hide the new tab page, but if you prefer disabling the feature permanently, here's how:
Step 1: In the Firefox address bar, type about:config and hit Enter.
Step 2: When the warranty warning appears, click on the "I'll be careful, I promise!" button.
Step 3: Type browser.newtab.url in the search box.
Step 4: Double-click on the preference name, then change the string value from about:newtab to about:blank. Click OK to save.
That's it. Now when you bring up a new tab in Firefox, it'll be blank, rather than displaying the thumbnails of your most frequently visited sites.