Instead of "Without WWW" (which was fairly distracting), use some regular expressions to weed out any www., http://, etc people may put in the url.
Every time I click the box, it wipes out what I had.
You should probably make this happen only when the box contains the original prompt.
I'm not a fan of the "default" button on any site.
Either add some css to the submit button or create an image.
I just feel like the rest of the site is unique, don't ruin it with some default button that throws off the whole feel.
If you need any sample code for my suggestions, let me know.
Bruce