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Does your server not support the If-Modified-Since HTTP header? If it does, then the background image should only be loaded once by each client until the cache is cleared, unless you were dynamically serving the image for some reason.

Fancy new site. I like it, especially the homepage. My only suggestion would be to center the links on the homepage and possibly center the menu tabs at the top as well.

Also, the email image in the bottom right of your page (http://blog.opensourcenerd.com/email.png) does not load properly (mentioned above). If I use your normal domain (not the blog subdomain), the image loads just fine.