Please read this long, but highly interesting, article titled "Visual Decision Making" on how "beauty enhances usability" when it comes to people visiting your website. Here is a short quote from the article:
[R]esearch shows that website users are powerfully influenced by aesthetics, and that positive perceptions of order, beauty, novelty, and creativity increase the user’s confidence in a site’s trustworthiness and usability. Recent design writing and interface research illustrate how visual design and user research can work together to create better user experiences on the web: experiences that balance the practicalities of navigation with aesthetic interfaces that delight the eye and brain. In short: there’s lots of evidence that beauty enhances usability.The author of the article goes into various theories about why attractive websites have better reception by visitors, but the bottom line is that looking good is as important as functioning well.
Read the whole thing here.