Kiel, Germany  - Web browsers are not particularly loyal programs. When pushed, they reveal more about our surfing behaviour than we might prefer. A few tweaks can help protect your private sphere, but they do impact browser performance.

It's amazing just how well online shops understand the preferences of their buyers. Simply registering with an online website reveals much to curious third parties about your PC and the user's origins.

Want to see for yourself? One trip to http://www.anonym-surfen.com/anonym-surfen/test, a free self-diagnostic site, will show you have much of your data is there for the taking. Tracking services like Google Analytics are also dedicated to following and analyzing your behaviour.

You aren't completely helpless, though. Your browser can make it easier or harder for companies to collect that data. The default settings on browsers tend to reveal a lot of information, says Christian Krause from the Independent State Centre for Data Protection (ULD) Schleswig-Holstein in Kiel, Germany. That information is not in and of itself personally identifiable, but combined with other information can be used to create a user profile.

This includes information sent to the page being called up about which operating system and screen resolution should be used. That can be helpful for formatting the webpage properly.

Other functions are more problematic. Yet simply shutting them off isn't always the answer. Turning off browser functions can reduce surfing speed and convenience tremendously, explains Michael Knott from the online magazine netzwelt. de.

The "Referrer" function, for example, provides the current website with information about the last one you visited. This is helpful for example when filling out a multi-page form. Anyone considering that too intrusive can circumvent the referrer: In Opera select the option "Tools/Preferences/Advanced/Network." Firefox users can install the add-ons "No-Referrer" or "RefControl." Internet Explorer (IE) does not provide a deactivation function.

Cookies are files stored on a computer to establish which web page preferences the user wants. They allow a website to recognize a surfer every time he or she returns to the page. That makes it easier to work with favourite forums or other sites that are used frequently. Yet cookies are also excellent tools for websites to puzzle together a user profile.

"Third-party cookies" are considered especially problematic. These are the cookies typically set by advertisers using banners. Simply blocking them isn't enough: new techniques are blurring the lines between third-party cookies and normal cookies, Krause says. The smart move is hence to allow cookies for the duration of a session and block permanent storage.

Yet not all cookies are deleted in that process, Krause notes. One example of this are "Flash cookies," used to operate clip portals. IE's cookie management function is available under "Tools/Internet Options/Privacy/Advanced," while under Firefox 3 it is under "Tools/Options/Privacy." Under Opera it is under "Tools/Preferences/Advanced/Cookies."

Website elements composed in JavaScript are also capable of snooping around. Unfortunately, Web 2.0 applications rely on JavaScript, Krause explains. He recommends separate approval and denial of access. Firefox users can also take advantage of the add-ons "NoScript" and "AdBlock Plus." Opera uses a filter list to block out unwanted JavaScript. This type of targeted blocks is not available in IE.

Even those who make all of these adjustments are still personally identifiable, Knott says. The only way to prevent that is to falsify your IP address. This can be done using services like www. anonymouse. org or software like "JAP" (anon. inf. tu-dresden. de). They reroute the addresses through various computers so that visited websites cannot determine the user's actual origin. The catch: much slower surf speeds. (dpa)