Make Thunderbird3 not switch to firefox after clicking a link

"I'd recommend going with the ThunderBrowse extension. Lets you view links in the message pane.
Edit: Since you want the links to open in the background in a firefox window, try settingbrowser.tabs.loadDivertedInBackground totrue in Firefox's about:config. This should let you open any links sent from programs without bringing firefox to the front."

"THIS is the more permanent solution I think you're looking for - worked well for me, although you may have to repeat the exercise if you ever return Firefox to its default settings

First, type (or copy and paste) ""about:config"" (minus quotes) into the Firefox address bar and hit enter.

In the Filter bar, type (or copy and paste) ""browser.tabs.loadDivertedInBackground"" minus the quotes.

By default, the value of this entry is false. To change it, double click the entry and it will toggle so that the value reads true. Restart Firefox and you're done."