Having upgraded my computer to Windows XP Service Pack 3 I have been unable to access a particular website. When I go to the website a logon box appears where I need to enter my username and password. However, it keeps returning me to the logon page and does not accept my credentials. The site managers inform me that everything is working fine at their end, so the problem must relate to my computer. The website used to work perfectly fine before installing Service Pack 3. This problem does not occur on any other websites.

This problem is indicative of a cookies issue within the web browser. Most websites which require a user to logon employ a facility called cookies or sessions. This is a method used so that you can authenticate once (when the logon box is displayed) and then the website can remember that you have authenticated when you wish to view other protected pages. Without such a facility implemented, you would have to re-authenticate for every protected page you wished to view, as the website has no method to remember that you are authenticated when browsing between different pages. When you logon to a website, a cookie is set on the computer which contains a unique session identifier. Then when you visit any other page on the website, the web server (which hosts the website you are browsing) can read this cookie stored on your computer, together with the session identifier contained within the cookie. The web server maintains a record of each issued session identifier together with the user who is authenticated against that session identifier. If there is a match, this means the session identifier is valid and you have authenticated. The web server will then allow you to view the requested page. If there is no match, it means either that your session has timed-out (for example, when you log into internet banking but leave the window idle for a period of time, it automatically expires your session and logs you out for security purposes) or you have manually logged out of the session and need to re-authenticate.

At this point you may be thinking – “couldn’t I just copy a cookie from another person’s computer and then login using their account”. Yes, and this can work and is a potential vulnerability. However, the reality is that you could not easily copy a cookie from another computer and then place this onto your computer before the session has timed-out, or before the other person has realised and logged-out of their session! A larger risk is that your cookie’s data (e.g. session identifier) is stolen while traversing a network connection. There are many methods to mitigate such risks, such as encrypted HTTPS channels, which are beyond the scope of this discussion. If you are interested, have a read of the following article on Wikipedia: en.wikipedia.org/wiki/HTTP_cookie .

While the above discussion is interesting and does provide background, it does not address your question so we will continue our investigations. If there is a problem with your web browser storing cookies for the website that you are attempting to visit, that could be causing the problematic behaviour. As a starting point, we will try clearing all cookies and your temporary internet files. This procedure assumes that you are using Internet Explorer. Open Internet Explorer and then go to the “Tools” menu > “Internet Options” and click the “General” tab. Be aware, if you cannot see the “Tools” menu in the Internet Explorer window press the ALT key, as the menu may be hidden. Once you have opened the Internet Options and are on the General tab, look under the “Browsing” heading and click the “Delete” button. Tick all the boxes except the top option “Preserve Favorites website data”. Be aware, this process will result in all saved passwords, form data and other data which you may have inputted into web pages (and subsequently saved in Internet Explorer) being lost. However, this is the best way to troubleshoot the issue. Assuming that you wish to continue, click the “Delete” button. Once the process has completed restart Internet Explorer and check whether the problem continues.

If this does not resolve the problem then we need to check the security settings for Internet Explorer, as it may be possible that Internet Explorer is rejecting cookies from that website due to the security settings implemented in your browser. Go back into the Internet Options and click the “Privacy” tab. Make sure that the security level has been set to the default of “Medium”. Click OK to save and close the settings. Check whether the problem continues. If so, make sure you are still on the problematic website (this is important) and now return to the Internet Options then click the “Security” tab. We are going to add the website that you are trying to visit to the list of trusted websites. You should only do this if you are certain that the website you are visiting is trustworthy and not malicious, as this will allow that website to have greater privileges within Internet Explorer. On the Security tab click the “Trusted Sites” zone and the “Sites” button. You should see the website address already filled-in, as it picks up the website which is currently being viewed in Internet Explorer. Untick the option at the bottom of the window “Require server verification (https:) for all sites in this zone” and then click the “Add” button to add that site into the zone. Click “Close” and then OK. Restart Internet Explorer and check whether the problem continues.

If you have completed all the above procedures yet the problem continues the only reasonable option left is to attempt a reset of Internet Explorer. This is a last resort, as it will result in all your Internet Explorer settings being reset and customisations removed. In Internet Explorer go to the “Tools” menu > “Internet Options” and click the “Advanced” tab. Click the “Reset” button near the bottom of the Internet Options window. Tick “Delete personal settings”. Make sure you have a read over the effects of resetting as outlined in that window, as this will reset Internet Explorer into a very factory default state and may result in certain things (such as custom toolbar and alike) being disabled. Assuming that you wish to proceed, click the “Reset” button and then restart Internet Explorer. Check whether the problem continues.

Should you reach this point and the problem is not resolved then there is little else I can suggest, as it seems that Internet Explorer simply does not want to cooperate with that website. This is even stranger because the problem does not occur on any other websites, indicating something wrong between that website and your installation of Internet Explorer. In any case, your best option in this situation is to try using a different web browser. I recommend Mozilla Firefox, a free open-source web browser available for download from www.mozilla.com/firefox). Firefox is completely separate from Internet Explorer so the problem being experienced through Internet Explorer should hopefully not affect Firefox.