Ambiguous forms. So, do I type the http or not?

Is it just me? Each time I encounter a form that asks for my website URL, I spend a second or two wondering if I should type it with or without the http:// ; based on what the site looks like, I have a hunch on which one's better, and I enter(or don't) the http://

While most forms are/should be built to handle this, I've had a http://http:// happen a few times.