there is a couple of contradictions in your css code. One of these and an extra '}' cause the problem:
from
ul#cantact li{
position: absolute;
border: 1px solid #000;
}
}
delete the extra "}"
and you should remove also:
ul#cantact li#linkin a:hover {
background-position: 0 -426px;
}
ul#cantact li#twiter a:hover{
background-position: 0 -426px;
}
In the code you have already defined background-position as 0 0
in
ul#cantact li a:hover {
background:url(../Images/contact.png) no-repeat 0 0;
}
And besides, with the -426px horizontal setting the img won't reveal on the screen.