Firefox 10 (released on ) decided to auto-hide the Forward button when there's no forward.
Very annoying. Because, as you navigate among the pages, the movement of these icons is distracting.
there doesn't seem to be a built-in way to disable this auto-hide. A workaround to stop this behavior is to set the icons to small. Right click on a empty area in the tool bar, then choose 〖Customize…〗. Then check mark 〖Use Small Icons〗.
this workaround doesn't work in Linux for Firefox 18.0.2 (as of ).
Reference: 《Source Firefox 10 release notes》 https://www.mozilla.org/en-US/firefox/10.0/releasenotes/