Web browsers are flexible. The basic programme is capable of day-to-day tasks such as displaying text, pictures, sounds and videos, but every so often you'll come across a site with files your browser can't understand. Rather than get a whole new browser, all you need to do is install an add-on (otherwise known as 'plug-ins' or ActiveX controls') that helps your existing program deal with the new material - just like the pieces you might attach to a camera, but free!

Popular add-ons

Most of the common add-ons help your browser handle multimedia files, such as animations, audio broadcasts and panoramic images. Others do smaller, simpler jobs. For example, there's an add-on that makes your browser display fancy mouse pointers. The three must-have add-ons are Flash, Shockwave and RealPlayer. Chances are you've already got them, because they're included with Internet Explorer, but it's worth visiting their websites to check for newer versions.

The Flash player is used for animations - everything from simple buttons to interactive cartoons. It's produced by Macromedia (http://www.macromedia.com/). The Shockwave player is often confused with the Flash player, because it comes from the same company and does a similar job. Shockwave is more sophisticated than Flash and is often used for games.

RealPlayer lets you enjoy streaming audio and video - files that play as they are downloaded, rather than afterwards. This is used for Internet radio stations and live broadcasts and is produced by RealNetworks (http://www.real.com/).

Most of the other add-ons aren't worth worrying about until you come across a website that requires them. When you do, there'll usually be a link to the site that supplies the add-on.

• Acrobat Reader (http://www.adobe.com/) displays documents in Adobe's Portable Document Format (PDF files), which is used for electronic manuals and catalogues
• QuickTime (http://www.apple.com/quicktime/) plays video files in Apple's QuickTime format and lets you view 360-degree panoramas
• IPIX (http://www.ipix.com/) also lets you spin round inside 360-degree images
• Beatnik (http://wwww.beatnik.com/) is for music
• Comet Cursor (http://www.cometsystems.com/) is used to display fancy mouse pointers
• Viscape lets you explore 3D websites creating using VRML - Virtual Reality Modelling Language (http://www.superscape.com/)

Installing browser add-ons

Most add-ons are installed the same way as any other program - visit the company's website, find the download page and download the program file on to your hard disk. Log off and close all your browser windows, then double-click the file you downloaded to start the installation routine. Then just follow the on-screen instructions.

Internet Explorer add-ons sometimes install automatically. For example, if you visit a site that requires the Comet Cursor add-on, the first thing you'll notice is a security warning asking whether you want to install it. Click Yes to proceed, or No if you'd rather not. If you click Yes, the software is integrated into your browser.