Here's a page I found that has some information on URL encoding (You know those "%20"s you see in URLs sometimes).
I could be wrong, but I think that Safari does not do this on the fly. I ran into a problem recently with a script I wrote that was relying on the browser to automatically encode the URL. IE did it just find – Safari choked. In any case, I'll be using the link above to manually encode the URL so Safari is happy.