The false/red "x" image that is displayed when there is an error with a report seems to be broken sometimes. It looks like something is appending a random ID to the end of the image filename:

<img alt="False" height="18" src="/images/false.png?*1258747171*" width="18" /><a href="/hosts/8/report">9 minutes</a>

This results in a 304:

[23/Nov/2009:22:07:54 0600] "GET /images/false.png?1258747171 HTTP/1.1" 304 - "" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)"

However, if I replace those numbers with something else random, the image works correctly. So, it must be something specific to the number that is being generated?