Hi, it seems your Right Side div
margin
is creating problem...
Please try modifying your CSS as below...
.HeaderRightDiv
{
position:relative;
top:36px;
left:40%;
width: 40%;
height: 54px;
margin-right: 100px;
border:3px;
background-color:#000;
margin-top: 0;
}
.HeaderRightDiv ul
{
margin-top: 0;
}
.HeaderRightDiv ul li
{
margin-top: 0;
}
.HeaderRightDiv a
{
margin-top: 0;
}
Hope this will help...