This article describes causes and solutions for the error "The page isn't redirecting properly. Firefox has detected that the server is redirecting the request for this address in a way that will never complete. This problem can sometimes be caused by disabling or refusing to accept cookies." For other errors, see Websites don't load - troubleshoot and fix error messages.
Web pages will often redirect you to another page. For example, after logging in to a site, you may be redirected to where you were before you logged in. What Firefox is telling you is that the site is redirecting you in a loop - for example, Page A sends you to Page B which sends you to Page A...
It may just be that the website has a bug. You can use Firefox's Report Broken Web Site feature to alert the Firefox developers of the problem. If the problem is specific to Firefox and enough people report the site, the Firefox developers may contact the website's owner themselves to help them resolve the issue. To report the website:
On the menu bar, click on the Help menu, then select Report Broken Web Site....
On the dialog that appears, fill in information about the problem.
Click Submit Report.
You can also contact the website's owner yourself.