If your web site doesn't look professional, no matter what product you're offering, your chances of success are minimal. The main page of your web site should be under 60KB in size and take only 30 seconds to load. If a page takes too long to load, your potential customer will not wait. Ultimately costing you business. Be cautious when selecting background and text colors.
Busy backgrounds make text difficult to read and draw the attention away from the text.
Always be consistent with your background theme on each page of your site. Use minimal animated graphics. These can be very distracting and can cause your page to look unprofessional. Personally, I think that banner exchanges do have their place, if you do it right. Try to avoid placing banner exchange banners at the top of your page.