Filter is Stripping URL with custom scheme There are times we are using custom schemes for URLs and storing them in Drupal 6.

The href attribute values are getting stored in the db properly.

So, 

&lt;a href="mycustomscheme://foo/bar"&gt;


gets stored as it's written. However, when viewing the page the unknown scheme gets stripped so it outputs:

&lt;a href="//foo/bar"&gt;


I've disabled all filters in the full HTML input format and have returned out of my hook_nodeapi function in my custom module, and disabled the WYSIWIG, and still the scheme gets stripped.

Any ideas where this might be happening?
I wouldn't recommend hacking the HTML filter in core. If you want you could copy/modify it into your own module and create your own filter, here is a link to a blog post that should help get your started.

Or you could try one of the contrib packages like Custom Filter.