User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_3) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.65 Safari/537.31 Steps to reproduce: Fixed element positioned off-screen with a negative top position. Also being centered with left: 50%; and a negative left margin. When the user scrolls, we trigger a class that brings the fixed element into view with a top position of zero. Actual results: The fixed element slides down (as expected) but appears slightly off center. Here's is an example: http://codepen.io/ggilmore/pen/9a119ace8bd6c659322af0c8a3396988 and here it is without the transition, positioned correctly: http://codepen.io/ggilmore/pen/b0aae89c1b78981d4a4fd763417c171e Expected results: The fixed element should transition into view and remain centered. The element snaps back into its target position when resizing the window. This appears to have been introduced with FF 20.
Solution found by adding an additional element and using margin: 0 auto; to center that within a 100% width fixed element. http://codepen.io/ggilmore/pen/363ca02b63fffab39758e660d45d325d
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