Ya it matters...plus a good designer can easily make a site look good in a short space time.
If you design quality stuff all the time it becomes second nature, but initially is a pain in the arse and believe I've asked myself what you're asking lots of times.
My last employer wanted my designs to improve every time I did a new one. Bastard was never happy but looking back at my portfolio I could see an clear improvement over the space of a year.
Start as you mean to go on is what I say
