put your content on different div's then when a link is clicked you would use javascript to hide one and show the other.
Code:
function Vis()
{
document.getElementById('content').style.visibility ='visible';
document.getElementById('content-container').style.zIndex =10;
document.getElementById('content').style.display ='block';
}
function noVis()
{
document.getElementById('content').style.visibility ='hidden';
document.getElementById('content-container').style.zIndex =3;
document.getElementById('content').style.display ='none';
}
The down side to the increased load time. All the content for all the pages must be loaded for this to work.
Is it really that necessary NOT to have it refesh?