title: Advantages to using URLField over TextField?
body: <p>As I understand it you should always use a <code>TextField</code> for a variable length string when your using a PostgreSQL database because the speed difference between a <code>TextField</code> and a <code>CharField</code> is negligible with PostgreSQL.  I'm relativly new to Django, and was considering using a <code>TextField</code> for variable length urls in my database. I was wondering if there are any advantages to using the <code>URLField</code>?  Would it be considered bad form to use a <code>TextField</code> rather than a <code>URLField</code> for urls?</p>