I was using Internet Explorer recently to check the route to the Cribb's Causeway shopping mall at Bristol, UK. I have used the Hotbot search engine since it was highly recommended in one of the very first issues of ComputerActive magazine (around 10 years ago), and I entered the search target simply as "Cribb's Causeway". I selected a likely-looking entry in the list that appeared, only to find the results page of another search engine. I hit IE's Back button to return me to Hotbot (without clicking on any of the links), but instead found myself staring in disbelief at a page of pornographic images, headed "Women seeking men". I then tried to go back by selecting Hotbot from the list displayed from hitting the small down-arrow next to the Back and Forward buttons. I was even more amazed to be taken to a page that told me my computer was riddled with malware, which I could remove by downloading software called MalwareAlarm. I declined this offer and instead scanned my PC with AVG (which confirmed it had no viruses), followed by Spybot and Ad-Aware. These found the usual crop of undesirables, including a cookie from MalwareAlarm. This latter, it told me, would declare exactly what I had seen, finding many false instances of malware that could only be removed by purchasing a licence for the software!
So, first and foremost, don't be fooled if this happens to you. Always be suspicious. But also, how on earth did a page of search engine results hijack my browser like that? I finally got my directions to Cribb's Causeway, but I had to restart IE - and for good measure I also restarted my PC. Surely this highlights a serious hole in Microsoft's security?
A further thought is this: if it happened to me, it could happen to a child using your computer. Take sensible precautions!