a.link_icon_left, a.link_icon_right{
    background-repeat: no-repeat;
    display:inline-block;
    line-height:22px; /* check your icon height */
}

a.link_icon_left{
    padding-left:20px;
    background-position: center left;
}

a.link_icon_right{
    padding-right:20px;
    background-position: center right;
}

a.icon_add{
    background-image:url(icon/add.png);
}
a.icon_delete{
    background-image:url(icon/delete.png);
}
a.icon_edit{
    background-image:url(icon/edit.png);
}
a.icon_detail{
    background-image:url(icon/detail.png);
}