Build Identifier: http://hg.mozilla.org/mozilla-central/rev/7eb1a56eaaf1 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:9.0a1) Gecko/20110823 Firefox/9.0a1 ID:20110823030804 Back Button/Alt+left arrow/Alt+History+Back do not work on certain site. This is not a recent regression. But Google Chrome works properly. Fails: Firefox 1.5.0.12eol Firefox 2.0.22pre Firefox 3.0.19 Firefox 3.5.19 Firefox 3.6.20 Firefox 4.0.1 Firefox 5.0.1 Firefox 6.0 Firefox 7.0b Firefox 8.0a2 Firefox 9.0a1 Opera 11.50 IE9 Works: Google Chrome 13.0.782.215 Reproducible: Always Steps to Reproduce: 1. Open Firefox with clean profile 2. Open Page (ex. "http://www.mozilla.com/en-US/about/") 3. Open URL( http://www.facebook.com/Firefox ) in a same tab. 4. Click Back Button in Navbar Actual Results: Back Button do not work Expected Results: Document navigation should work properly

This is back-button trapping, and is probably covered by one of the dependencies of bug 340021.