>>> My Info: Win7_64, Nightly 49, 32bit, ID 20160526082509 STR_1: 1. Open attached "testcase 1" 2. Place text caret between symbols n and ' 3. Press Delete 4.(bonus) Keep pressing Ctrl+Z, Ctrl+Y to see the effect better (because caret won't blink) AR: Step 3 - Caret teleports by 1px to the right ER: Caret shouldn't move Note: I encountered this bug on https://vk.com/ when I was typing some text

The testcase seems to be missing.

The Roboto font that you have embedded in the testcase includes a kern between the "n" and "'" glyphs. This in effect reduces the advance width of the "n" when it is followed by "'", and therefore the caret in the sequence "n'" appears one pixel further left than in the sequence "n ". You can confirm that this is what's happening by adding "font-kerning:none" to the style; that will prevent Firefox applying the kern that's in the font, and the effect you're seeing will no longer occur. So this isn't a bug, it is behaving correctly (although I'd question the wisdom of including such a kern in the font; I don't think the resulting spacing in the "n'" sequence looks good).