You've not told us which browser you're using. If it's Internet Explorer, see if anything here helps:
http://answers.microsoft.com/en-us/ie/forum/ie8-windows_other/back-arrow-not-working/ce43d94e-3de0-48c1-82d3-a7f88e4f7d64
(That page refers to IE8 but the information probably applies to other versions of IE as well).
Remember that pressing Alt together with the left-arrow key does the same job as clicking on 'Back'. It might be worth a try.
Remember as well (if you believe that you might need to return to your original page) that right-clicking on a link enables you to open the link in a new tab, which you can then close to return to the page you were viewing before. (That's what I usually do; I hardly ever need to use the 'Back' button).
Lastly, remember that there are lots of different browsers available (with nearly all of them being vastly superior to Internet Explorer). Most of the 'regulars', here in AB's Technology section, wouldn't touch Internet Explorer with an infinite number of proverbial bargepoles. Firefox is much better:
http://www.mozilla.org/en-US/firefox/all/
Chris