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.

Answer 2

I'd recommend you to specify top:0; left: 0; to your ::before pseudo elements. Sometimes cheeky browsers take a few px up and left to the actual position. CSS:

.like:before {
    float: none;
    width: 30px;
    content: "like";
    margin: 0px 10px 0px 0px;
    padding: 0px 5px;
    background-color: #FF7373;
    color: #FFF;
    border-right: 1px solid #CCC;
    position: absolute;
    top: 0;
    left: 0;
    border-radius: 4px 0 0 4px;
}
.like {
    float: none;
    height: 30px;
    border-radius: 4px;
    box-shadow: 0px 0px 1px rgba(0, 0, 0, 0.5);
    padding: 0px 10px 0px 0px;
    margin: 12.5px 10px;
    background-color: #000;
    font: 16px/30px arial;
    color: #FFF;
    border: medium none;
    position: relative;
    width: 88px;
    text-align: right;
}

Fiddle: http://jsfiddle.net/79cEb/13/

Answer 3

Maybe try positioning the like absolutely using CSS

.like{
float: left; 
height: 30px; 
margin: 12.5px 0; 
background-color: #FAFAFA; 
border-radius: 4px; 
position:relative;
padding: 0 10px 0 40px; 
margin: 12.5px 10px; 
background-color: #000; 
font: 16px/30px arial; 
color: #FFF; 
border:none;}

.like::before{
position:absolute; top:0; left:0; 
width:30px; 
content: 'like'; 
margin: 0 10px 0 0; 
padding: 0 5px;
background-color: #FF7373; 
color: #FFF; 
border-right: 1px solid #CCC; display:block; border:0;
}