Rumors say that Firefox 3 will have the long expected full page zooming feature. It will be able to zoom in the images as well, just like you can do with Opera and IE7.

This specific feature request was originally suggested in Bugzilla, 8 years ago, but was delayed and eventually bypassed since it was not considered practical in today’s HTML rendering engine for Firefox (Gecko 1.8). Like I said above, this feature is scheduled for inclusion in Firefox 3 since the new version of Gecko (1.9) will also include a large number of significant improvements.

Even if the feature is fully implemented and functional, the regular interface does not show the functionality to the regular user.
In order to test it out, you have to use Firefox’s built-in JavaScript error console, and here’s the code sequence you need to validate:

Components.classes["@mozilla.org/appshell/window-mediator;1"]
.getService(Components.interfaces.nsIWindowMediator)
.getMostRecentWindow(”navigator:browser”).getBrowser()
.mCurrentBrowser.markupDocumentViewer.fullZoom = 3;

This experimental code will zoom the current page you’re browsing to 3x. You can also experiment with different values so you can see different levels of zoom. For zooming out, use decimals like 0.5 for example.

This is yet another example of how brilliant Firefox 3 is.