I've sent out some link exchange invitation e-mails - but the edit link included in these e-mails doesn't work. This is the link specified by %EDITURL% in the e-mail template. What's wrong?

Under Change Settings >> Site Settings, near the bottom of the page is a checkbox labeled Site Supports HTTP Local Access. Read the information below this checkbox and click on the test link. If the test shows that your web server does not support http local access, check the checkbox and click Submit Changes. Your %EDITURL% links should now work correctly.