If you are not able to enter directly to the pay site like http://user:pass@www.porn.com/memb... and you have to enter the information manually, you need to download the IE patch. Information is available on this patch at Microsoft's Website. Below is a link to a zip file which contains registry fixes to disable and if you wish re-enable the new invalid URL syntax. Both are completely safe to use and will make this site and other password sites easier for you to use. Please download this file, unzip and click the addurlfix.reg file to fix the invalid links or the removeurlfix.reg file to re-enable it.
