Topic on Extension talk:Categorize

The "jumping" of the buttons while hovering with the mouse is caused by the CSS which sets the border-width of the buttons from 1px to 2px without compensating by reducing the padding of the elements accordingly. To amend this the following CSS recreates the same effect by using "outline" instead of "border" which doesn't affect the box size of the element:

span.xlabel:hover, span.xselected {
  border-width: 1px !important;
  outline: 2px solid #666666;
}

span.xselected {
  outline-color: red;
}

There's some horizontal movement left due to making the selected button bold.