Hot on the heels of last week's reveal of Firefox 3.7 concept screens, Mozilla has now posted potential designs for 4.0 on its blog.

It's only been weeks since the release of Firefox 3.5, but as ever Mozilla is keen to push the envelope.

Marked as a draft page, the designs vary between a simple enhancement of the current design to a more radical Chrome-alike redesign with the tabs on top (below).

Firefox 4.0

Mozilla says that while this saves space and mouse movements, it would be confusing to many existing users, as well as hiding the page title.

Firefox 4.0

The page at the Mozilla Blog also features other small enhancements currently under debate. Nothing is set in stone, and Mozilla says it is welcoming comments on the designs.