if (document.images) {
    webmailbuttonup       = new Image();
    webmailbuttonup.src   = "images/webmailbutton.jpg" ;
    webmailbuttondown     = new Image() ;
    webmailbuttondown.src = "images/webmailbuttondown.jpg" ;
    
    portfoliobuttonup       = new Image();
    portfoliobuttonup.src   = "images/portfoliobutton.jpg" ;
    portfoliobuttondown     = new Image() ;
    portfoliobuttondown.src = "images/portfoliobuttondown.jpg" ;
    
}
function buttondown( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "down.src" );
    }
}
function buttonup ( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "up.src" );
    }
}