Styling af knapper

CSS kode 

 body {
     background-color: #167cc6;
     font-family: "Comic Sans MS";
 }
 input.gem {
     display: block;
     width: 100px;
     height: 50px;
     background: url(../img/submit.png) no-repeat 0 0;
     outline: none;
 }
 input.gem:hover {
     background: url(../img/submit.png) no-repeat 0 -50px;
 }
 input.gem:active {
     background: url(../img/submit.png) no-repeat 0 -100px;
 }
 input.ryd {
     display: block;
     width: 100px;
     height: 50px;
     background: url(../img/submit.png) no-repeat 0 0;
     outline: none;
 }
 input.ryd:hover {
     background: url(../img/submit.png) no-repeat 0 -50px;
 }
 input.ryd:active {
     background: url(../img/submit.png) no-repeat 0 -100px;
 }
 input.knap {
     display: block;
     width: 100px;
     height: 50px;
     background: url(../img/submit.png) no-repeat 0 0;
     outline: none;
 }
 input.knap:hover {
     background: url(../img/submit.png) no-repeat 0 -50px;
 }
 input.knap:active {
     background: url(../img/submit.png) no-repeat 0 -100px;
 }

HTML kode 

 <form name="custombuttons" action="#" method="POST">
             <input type="text" name="felt1" placeholder="felt1" /><br />
             <input type="text" name="felt2" placeholder="felt2" /><br />
             <input type="text" name="felt3" placeholder="felt3" /><br />
             <textarea name="felt4" placeholder="Tekst skrives her..."></textarea><br />
             <input type="submit" name="submit" class="gem" value="Send/Udfør" /><br />
             <input type="reset" name="reset" class="ryd" value="Slet/Ryd" /><br />
             <input type="button" name="button" class="knap" value="Knap" /><br />
         </form>