I want to do extension of my firefox app but can't do it please help to that

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There is an annoying white flicker when opening up a new tab if i use this :/.

IT SUCKS!!!

Funciona perfecto, muchas gracias. Works great, thank you very much.

Works perfectly and provides all the control over new tab placement and contents that I've been needing. Honestly, this functionality should just be an integral part of Firefox, but it's great that someone has taken the time and care to add it.

Thank you for this! I simply wanted my home button to open google and land in the search box so I could type. I found this impossible to do until this add-on. It would default to the address bar and required several "clicks" to get where I wanted to be. A simple thing I know but now it behaves the way I like it too. Thank you!

Even after changing color, it pops up white shining through the night and just after that colors the tab black.