Screen flickering with tight line ends
Sometimes there is flickering when hovering the mouse over the first word in a line, if its width changes very slightly and that makes it fit the previous line.
Here is a short screencast of the problem: https://dl.dropboxusercontent.com/u/49287747/Screencast%202015-03-03%2012%3A27%3A45.mp4
This happens using Firefox 38 in Linux. I don't know if the tiny size change of the word is a Firefox bug or it's a CSS issue that can be solved.