User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b5) Gecko/2008032620 Firefox/3.0b5 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b5) Gecko/2008032620 Firefox/3.0b5 No error, it simply does not open in the sidebar. The same thing happens whether it is a target attribute in the html A tag, or a window.open in javascript. Editing the properties of a bookmark to check "Load this bookwark in the sidebar" does work. Reproducible: Always Steps to Reproduce: 1. click on the "launch" hyperlink Actual Results: opens a new window with the requested URL (or new tab depending on browser options) Expected Results: opens the requested URL in the sidebar.

Also see bug 438526