WWB is normally very good at not providing duplicate names, unless you go back and edit the Master page after it has been associated with other pages. Then, of course it has no way of knowing that you've added (for example) extra images which, because you didn't rename them),have the same name as ones in your published pages. Then, when you publish it, the browser gets a bit confused.
Of course, this should be obvious to the experienced web builder, but it can catch anyone out. And don't ask me how I know this


I hope this helps.
Alan