In the past, I've found that looking at a site for long periods of time during development caused me to overlook simple errors and other items that could be improved. Having a third party review your site prior to publishing or updating can help out greatly.
There are a few different types of people you can and should get to take a look at your site.
1. Someone who is not strongly interested in the content of the site. By having this type of person look at your site, you are representing the average web surfer who happens across your site. My wife is normally the one who fits the bill for this one.
2. Someone who is interested in the subject matter of the site. This represents someone in your target audience. If you are running a comic book site, this would be a comic book fan. If you are running a wedding clothing website, it would be someone who is about to get married. You get the idea. For me, this person (obviously) varies each time.
Even if I'm fortunate and working on a website that interests you personally, you should still get a third party that is also interested in the subject matter to take a look at the site.
3. A fellow webmaster. While you may not consider yourself having mastered the web, you are the master of the website you are working on. Have other webmasters and web designers take a look at your site.
One good resources for this is The Webmaster Forums (http://www.webmaster-forums.net). Just review a few sites yourself first, and then you can post a site for others to review. (This is subject to the rules on their site, so be sure to read any and all guidelines first.)
Having some other people take a look at your website before you upload it (or upload changes to it) is a great idea. Not every little change will require that you do this, but at least have it checked out a couple of times a year.
Tim is the owner and senior web designer at T&S Web Design. His company has developed and maintained website for dozens of small businesses and organizations. Tim also maintains a blog with free website advice for small business owners, GetASiteOnline.com.