The just-released beta 4 version of Firefox 3.0 shows a browser short on flash and long on important, useful improvements that make browsing the Web easier, faster, safer, and simpler to customise.

Firefox 3.0's primary interface has been modified somewhat to look more modern, but much more important are a host of less immediately obvious features that any serious Web surfer will welcome.

Firefox 3.0 beta 4 offers a few visible additions to the browser. For example, the download manager has been improved, making it simpler to locate and work with downloaded files. It's quite nice – you can easily search through your downloads.

Also, Firefox 3.0 now integrates directly with your virus scanner, and shows the scanning being done right inside the download manager. And you can see the icon of the file you've downloaded, making it a lot quicker to identify.

The zooming feature, already improved in previous betas, has been refined. With Firefox 3.0 beta 4 you can now, if you wish, zoom in and out of the text (rather than the entire page); your settings are remembered, so you don't have to reset them each time.

In addition to visible features, there are a number of key changes to be found under the hood. Firefox has long been bedevilled by memory bloat problems, and with Firefox 3.0 beta 4, Mozilla claims that it has gone a long way toward solving that. It claims that it has plugged hundreds of memory leaks.

In addition, Mozilla says that it has cleaned up a related memory issue: that the browser uses increasing amounts of memory the longer it's in use. Mozilla says that Firefox 3.0 beta 4 collects and releases unused memory, and reduces memory fragmentation.

Without running lab tests, we can say Firefox 3.0 beta 4 seems faster and does not slow down over time, as did previous versions. We tested the version for Vista; the version for XP shouldn't be much different.

Better browsing and bookmarking

Other changes to Firefox 3.0 have already been available in previous betas, but are worth mentioning. The most visible is the more modern-looking upper left corner with its icons for forward, back, reload and stop. The forward and back buttons now have a 3D chiselled look, bringing what had been a tired-looking 2D interface into the modern age.

One not-so-nice change: Mozilla has moved the Home button off of the Navigation toolbar and on to Firefox 3.0's Bookmarks toolbar. This may have freed up some real estate on the Navigation toolbar, but it means that if you normally hide the Bookmarks toolbar, you no longer have access to your Home button. The change does not make much sense.

That being said, Firefox 3.0 has done an exceptional job of turning the Navigation toolbar into a highly useful and powerful tool by integrating it with bookmarking and security features. For example, there is now a star icon on the far right side of the address bar; click it and you'll bookmark the site you're currently visiting. When you bookmark the site or visit a site you've already bookmarked, the star is gold; otherwise it is grey. To edit the bookmark – for example, to change its folder, add tags, and so on – click the star after it's turned gold.

Also useful is a new search-as-you-type feature. As you type an address into the Address Bar, a drop-down list of sites you've visited and in your bookmarks appears. The list includes not just the site URL, but also the site name and favicon.

Similarly, when you're visiting a site on which there is an RSS feed, an RSS icon should show up, as it did in the previous version of Firefox. (In this beta, we found that the icon did not always show up on pages with RSS feeds.)

There is a handy new security feature tied to the Address bar. Click the favicon of the site you're visiting (located on the leftmost side of the Address bar), and you'll be told whether it has been "verified" as being the site it says it is, using its Extended Validation (EV) SSL certificate. As a practical matter, verification doesn't mean much right now; very few sites use those certificates. However, some, such as PayPal, do, and hopefully more will in the future.

More useful is that you can click the More information button that appears with the verification, and a tabbed dialogue box pops up, allowing you to get a great deal of information about the site – whether you've visited the site before, whether it uses cookies, whether you have a password on the site, and so on – and be able to view the cookies and passwords. In addition, you can customise how you browse the site, setting such features as whether to allow pop-ups and cookies, and whether to load images.

Better security and more

Firefox 3.0 beta 4 includes other security features as well, including protection that warns you if you're visiting a site known to host or install viruses, spyware, Trojans or other malware. Firefox now tells your antivirus software that it's downloading a file, so that your software can check it. It also disables old, unsafe Firefox add-ins and extensions.

The browser integrates better visually with whatever operating system it is installed on by using OS-specific icons and toolbars, and taking on more of the operating system's look and feel. Other changes include better management of plug-ins.

There are many features for developers as well, including one that could be very important for users. Mozilla says that Firefox 3.0 can be used for offline functionality with sites such as Gmail, although site developers have to add offline support in order for users to take advantage of it.