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When I reload the webpage, the overlay is removed. I then have to check it again. The overlay position will be lost.
The problem occurs regardless of chosen tab in firebug. It also occurs when reloading the page without having firebug open.
This plugin is really great one, but I cannot use it like this. The overlay has to stay until I choose to remove it.
I am aware of the fact that this bug has been reported before, but I cannot find it any longer. People has also been able to reload the webpage and keep the overlay if the pixelperfect tab has is choosen, which is not the fact for me.
As a workaround, have you tried the "Lock?" option?. If you turn on the overlay and then toggle the lock you can inspect and make changes without having to refresh the page.
This bug will be fixed in v2 which will be out in the coming months.