We are asked this question all of the time - "What is the perfect design width for our Website?" Thanks to several great articles on this issue there are some great answers, but I also like to counsel our clients, designers and developers that like all aspects of the Website, you gotta know who's coming to your site specifically. You need to make your Website accommodating and accessible.Google Analytics, WebTrends, (Adobe) Omniture and even your old Web server logs will tell you some very insightful information on who's viewing and how they are doing so.
This article, Is There a Perfect Web Design Width?, by Five Fingers Coding, shows great statistics on a more universal scale from W3Counter where the optimal design size is trending.
For more on this topic, also read some articles from the past:
