There is much to say about web design because design is an important factor in online marketing, but the biggest mistake most business owners make regarding web design is putting the carriage before the horse. I can't tell you the number of times prospective clients call me for search engine marketing right "after" their web designer finishes building their website. The problem with this approach is that 90% of graphic designers are trained to make websites pretty, but they don't know about conversion. If you don't incorporate conversion optimization into the design of your website, it won't matter how attractive the site is if it can't convert a visitor into a paying customer, client or patient.
When I get these calls I know what's coming next because I'm the one who has to break the bad news... I have to explain to them that their new beautiful website needs to be modified if they want me to get results for them. Sometimes the modifications are minor, but other times they are more than the business owner wants to pay for because they just paid a designer a ton of money for a beautiful website and simply don't want to hear that. In these cases I tell them I won't be able to help them. It doesn't bother me so much that I have to give them the bad news. What really bothers me is that they go away thinking I'm making this stuff up to charge them more money.
Before you invest in the redesign of your existing website, or the design of a new website, do yourself a favor and talk to a search engine marketing expert first. This will save you headaches and aggravation - not to mention money - because you'll be able to incorporate the important marketing components your website needs to make you money. The formula is: Traffic + Conversion = Profit.