document.write( '<span class="loadingbar" ID="loadingbar"><p>Loading Data... </p>' );
document.write( '<img id="loadingbarimage" src="Images/loading.gif" />' );
document.write( '</span>' );

#loadingbar{
position: fixed;
display:block;
top: 15%;
left: 50%;
margin-left: -10px; /* half of the width */
z-index: 9999;
width:200px;
}