firefox adds strange space arround Pseudo-elements

Question

Take a look at these photos
JSFiddle link at the bottom

firefox:

Answer 1

I made you this solution, it places the button relative and the :before class absolute. Then you can use the top, bottom and left position, which will be relative to parent.

Note that I added a overflow: hidden to the button, so the rounded borders are still visible.

This is the altered CSS:

.like {
    float: left;
    height: 30px;
    margin: 12.5px 0;
    background-color: #FAFAFA;
    border-radius: 4px;
    box-shadow: 0 0 1px rgba(0, 0, 0, 0.5);
    padding: 0 10px 0 40px;
    overflow:hidden;
    margin: 12.5px 10px;
    background-color: #000;
    font: 16px/30px arial;
    color: #FFF;
    border:none;
    position: relative;
}
.like::before {
    float: left;
    width:30px;
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    content:'\F011';
    background-color: #FF7373;
    color: #FFF;
    border-right: 1px solid #CCC;
}

Also, see the updated Fiddle.