I wanna put a span within an a tag that covers all the same space(I mean the span with same space(width and height) of tag)
<a class="a-tab">
   <span class="fa fa-fw fa-plus">
</a>
.a-tab{
     float: none;
     display: inline-block;
     color: #333333;
     padding: 0.571em 1em;
     font-weight: 700;
}
.fa-fw{
    width: 1.28571429em;
    text-align: center;
}
.fa {
    display: inline-block;
    font: normal normal normal 14px/1 FontAwesome;
    font-size: inherit;
    text-rendering: auto;
    -webkit-font-smoothing: antialiased;
 }
so the problem is that I can't change the  tag because it's from a lib and the fa plus icon. The only thing I can change is the <span>, maybe with a <div>. But it seems doesn't work. I tried to put a width: 100% and height: 100% but still not works.
Any suggestions?