Buttons in IE11 are normally highlighted in cyan when hovered over, but adding a CSS rule with the :hover pseudo-class can cause this hover effect to break and buttons to exhibit strange behavior when clicked. In a simple JSFiddle test case with basic HTML containing only two buttons labeled "Prev" and "Next," the buttons work as expected.
Hovering over the "Prev" button gives this appearance:
https://i.sstatic.net/IdAWK.png
https://jsfiddle.net/qtsfokmy/
However, by adding an arbitrary CSS rule using the :hover pseudo-class, such as .AnythingYouWant:hover {}, the hover highlighting on the buttons is disabled. Clicking a button then causes the hover effect to get stuck even after moving the cursor away.
https://jsfiddle.net/vwhurLy4/
These issues were observed on a Windows 7 64-bit SP1 machine running IE11 11.0.9600.18230 with the Aero Theme enabled. It appears that Firefox and Chrome do not have the same problem with the :hover CSS rule, raising questions about whether this behavior is an IE11 bug or a result of invalid CSS implementation.