The site is 404'ing so I can't search there. I've tried looking at the docs but it isn't really clear where I might find it. I have made a config with the list of tags I want to allow and included <a> but HTML Purifier removes the href. What do I need to add to the config to allow the href as it is in the default settings of HTML Purifier?
-edit-
This is what I have now:
$config = HTMLPurifier_Config::createDefault();
$config->set('HTML.AllowedAttributes', 'a.href');
$config->set('HTML.Allowed', 'various tags');
$config->set("HTML.Nofollow", true);
$config->set('CSS.AllowedProperties', '');
Adding $config->set('HTML.AllowedAttributes', 'a.href'); did the trick. However, I would like to hear Edward Yang's thoughts on the matter as he believes it shouldn't be necessary according to his reply.
Href is allowed by default. What is more likely is that you have magic quotes accidentally enabled. Turn them off.
(P.S. The website is down because Dreamhost sucks, and ate its disks. We're waiting for them to finish recovery...)