Fixing the RSS feed so that it passes validation

Current Functionality:
The RSS feed does not validate. Some blog aggregators, such as Alltop.com, reject sites that don't pass RSS feed validation.

Testing:
You can test the validation of an RSS feed here: http://validator.w3.org/feed/

Example:
Nate's site doesn't validate.

Source: http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fnatewienert.com%2Fposts.rss

Desired functionality:
RSS feed should pass the RSS feed validator.

Example:
My site, which has this fix, does validate: http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fwww.lauradhamilton.com%2Fposts.rss