Simple Base URl rewrite

Thanks for the quick reply. I definately do not want the browser to know they are going to def as they couldn't resolve it anyway but if there is a link within the web stie to another page I assume they would click and the request would send the browser to the real url def. In this case the traffic being sent back ot the user would have the def in it and the browser wouldn't know what to do with it? Am I correct or am I just confusing myse3lf here?