I've had few designers that handed me the design in html/css and it looks fantastic. Then when I start to drop in the code behind I find all types of things broken. Usually these are cascading reflow errors. They put in a few lines of Lorem Ipsums but the returned value might be a paragraph or be an empty field.

Now I have the impossible task of working my own code and fixing the shims the designer put in.

This doesn't happen that often but more than enough. Usually, only the designers that know enough HTML to think it's like Photoshop attempt this. Most others treat it as the markup language it is, with loose constraints.