CSS

margin bottom not working

// Your problem is that link ("a") is an INLINE element and you cannot set margin to inlines elements. In order to make it work, you have to declare it as BLOCK element, by adding:

 a{
  display: block;
 }

margin-top not working

.form_head {
    margin-top: 20px;
    color:#58585a;
    font-size:22px;  
    display:block; /* Add this */ 
}

margin-top not working

#outer {
    width:500px; 
    height:200px; 
    background:#FFCCCC;
    margin:50px auto 0 auto;
    display:block;
}
#inner {
    background:#FFCC33;
    margin:50px 50px 50px 50px;
    padding:10px;
    display:inline-block;
}