When I move (customize) the toolbar, joining the WebRep button at the top of Firefox, next Firefox restart, the button is gone… :-\ 
Strange that I have just had a play round with that Had to select the tabs on top first (don’t like that option) and I moved three items, WOT, Closed tabs list and webrep, image (top). Restarted firefox and WOT was still there, Closed tabs list (greyed out), image (bottom) and webrep to the left of the address bar (not shown in image)
Edit: If I uncheck the tabs on top option the webrep icon appears back on the tab bar line Closed tabs list (greyed out), but that is because after restarting there were no closed tabs (working after closing a tab).
So, we’re already two with the same problem.
I believe so but, we are using different firefox themes or skin, etc.
Your image doesn’t show much, I’m all for minimalist, but where are the rest of your toolbars (tabs, navigation/address bar) surely you haven’t got it all on that one line ?
I don’t think it will help that much… For me, everything is minimalist also…
Oh it makes sense to me now I see that you cropped the top off, as I saw the old style Minimise, Maximize and Close icons, I thought that was the top of the page and that was where I was trying to get them. The only way I could do that was by moving the tabs to the top, which I didn’t need to do.
Even so restarting firefox after the switch the avast webrep icon ends up on the Navigation Bar to the left of the address window. The other I moved stay were they were, now if this were a skin issue I would have expected it to be the same for the other icons I moved and not just the avast webrep icon.
Why avast is the only icon with problems? All the time…