User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1 Build Identifier: 4.0.1 Example. I open of "www.facebook.com" on one tab, I then open a new tab and type "f" which brings up a list of previous websites that had "f" in the url, "www.facebook.com" happens to be the first so i press the down arrow to highlight "www.facebook.com". I then press 'enter' and the tab closes and brings me to the existing tab with that url. If you manually type in the url again, it will let you go to it in that tab, but that is an annoyance. Reproducible: Always Steps to Reproduce: 1. Open browser 2. Go to a URL 3. Open new tab 4. Type the first letter of that same url 5. Scroll down the options to the same url 6. Hit enter Actual Results: closes the second tab and takes me to the first one

That first entry in the list is not of a previous website, that is the new "Switch to tab" feature in Firefox 4. See http://support.mozilla.com/en-US/kb/Location%20bar%20autocomplete#w_what-is-switch-to-tab

To duplicate a tab middle click or ctrl click on the reload button.