We have a weird problem and we can't figure out what's causing the issue.
Randomly, some of our visitors get the following error:
Authorization Required! – 401. This server could not verify that you are authorized to access the document requested.
We couldn't replicate the error, but some visitors repeatedly get this error message on a specific page (http://www.hairproducts.com/view_product.php?product=COL-SAT104&fg). Our website is written in PHP and runs on Linux. In .htaccess, visitors are supposed to be redirected to customized error pages (we tested it and it worked fine) but the visitors get a non-custom 401 error message.
We tested different locations and browsers, but haven't been able to reproduce the issue. We contacted our server admin, but they insist there isn't anything in the settings that would cause that kind of error for visitors. We checked our PHP pages and didn't find anything that might cause this error message. So now we are stuck.
Can anyone give us an idea about what might cause such a problem?
One more question: can external javascript files can cause such a problem, making a whole page show a 401 error message?