put an overlay on the page
#loading-mask {
background-color: white;
height: 100%;
left: 0;
position: fixed;
top: 0;
width: 100%;
z-index: 9999;
}
and then delete that element in a window.onload handler or, hide it
window.onload=function() {
document.getElementById('loading-mask').style.display='none';
}
Of course you should use your javascript library (jquery,prototype..) specific onload handler if you are using a library.