I can not completely say this new ‘feature’ was taken from Chrome. Presently Firefox has separate stop, reload and go buttons. There are many add-ons out there such as Stop-or-Reload Button which combine the stop and reload buttons in to one button. In the upcoming Firefox 4 this is taken a step further. The ‘go button’ (which appears at the right-end of the address bar when typing an address) is being moved off the address bar and merged with a combined stop and reload button. As I said this is sort of borrowed from Google Chrome. In Chrome on the right-side of the address bar is a combined stop/go button. In IE8, there are separate reload and stop buttons to the right of the address bar.

These screenshots below from Mozilla Links show the new ‘button’:

Reload button once page has fully loaded.

Stop button while the page is loading.

Go button while entering (or editing) an address.

Percy made an interesting observation:

While it should make more sense to new users, this is no doubt going to anger more than a few long time Firefox users used to clicking next to the back button to reload or stop the current web page.

I am not sure it really makes sense to combine all three buttons. I suppose you will gain a little bit of space on the toolbar. I also understand his point about placing it on the right-side as that is where these buttons are located in IE7 and IE8 and Chrome. But Safari has a combined stop/reload button on the ‘traditional’ left side as does the current versions of Firefox along with Opera. Personally, I never use the ‘go’ button (I simply press enter after typing in my address) and seldom do I use the ‘reload button, opting instead to press F5. The good news is you are not being forced to use the 3-in-1 button, it can be ‘uncoupled’ via the Customize Toolbar window.