you will need to do it like this...
<a type="button" href="http://www.facebook.com/" value="facebook" target="_blank" class="button"></a>
and add the basic css if you want it to look like a btn.. like this
.button {
width:100px;
height:50px;
-moz-box-shadow:inset 0 1px 0 0 #fff;
-webkit-box-shadow:inset 0 1px 0 0 #fff;
box-shadow:inset 0 1px 0 0 #fff;
background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #ffffff), color-stop(1, #d1d1d1) );
background:-moz-linear-gradient( center top, #ffffff 5%, #d1d1d1 100% );
filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#d1d1d1');
background-color:#fff;
-moz-border-radius:6px;
-webkit-border-radius:6px;
border-radius:6px;
border:1px solid #dcdcdc;
display:inline-block;
color:#777;
font-family:Helvetica;
font-size:15px;
font-weight:700;
padding:6px 24px;
text-decoration:none;
text-shadow:1px 1px 0 #fff
}
.button:hover {
background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #d1d1d1), color-stop(1, #ffffff) );
background:-moz-linear-gradient( center top, #d1d1d1 5%, #ffffff 100% );
filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#d1d1d1', endColorstr='#ffffff');
background-color:#d1d1d1
}
.button:active {
position:relative;
top:1px
}
target works only with href tags..