07 May 09 11:39 pm
Anywhere between 800px and 1024px is a good width for a website.
Banner sizes vary. If it's an advertisement banner, you may be restricted to the size you're given by the advertiser, or alternatively you may limit them to the size you allocated to a previous ad so the change is easy. Whilst the general shape seems common across the internet, the exact dimensions are usually made up by the website designer, or the ad provider.