It's always a plus to make sure that you give a link so we can see what you're looking at.
You can leave the URL field blank if you want. Normally one puts in the url of their own home site. Like I would put in the URL of my own blog, http://drmikessteakdinner.com/
The email and name fields are required though for a comment to go through.
Hope this helps,
-drmike
When my students go to post a comment it asks the kids to fill in the URI'?label> What are they supposed to type in?