When calc is involved in resulting style of "left", transition doesn't seem to take effect. http://jsbin.com/ehigic/11/edit In this example, checking the checkbox supposed to move the rectangle to left: -webkit-calc(50% - 100px); with transition effect but there's no effect happening. Confirmed it works when giving static number or view it on Firefox.
*** This bug has been marked as a duplicate of bug 86160 ***