If you're talking about an internet browser (e.g. IE or Firefox) then one thing to try is to clear the browing history, exit and restart the browser.
If that doesn't make a difference then you can always run the browser in safe mode (so that add-ons will be disabled); you will have to re-enable each of the add-ons afterwards but should this work then by enabling the add-ons one-by-one you might identify which one is causing the problem (if indeed any of them is responsiblefor it - it might be due to e,g, a faulty applet that only gets run once in a certain webpage).