if (document.images) {
    homebuttonup       = new Image();
    homebuttonup.src   = "graphics/home.jpg" ;
    homebuttondown     = new Image() ;
    homebuttondown.src = "graphics/homeover.jpg" ;

    aboutbuttonup       = new Image();
    aboutbuttonup.src   = "graphics/about.jpg" ;
    aboutbuttondown     = new Image() ;
    aboutbuttondown.src = "graphics/aboutover.jpg" ;

    clientsbuttonup       = new Image();
    clientsbuttonup.src   = "graphics/clients.jpg" ;
    clientsbuttondown     = new Image() ;
    clientsbuttondown.src = "graphics/clientsover.jpg" ;

    equipmentbuttonup       = new Image();
    equipmentbuttonup.src   = "graphics/equipment.jpg" ;
    equipmentbuttondown     = new Image() ;
    equipmentbuttondown.src = "graphics/equipmentover.jpg" ;

    capabilitiesbuttonup       = new Image();
    capabilitiesbuttonup.src   = "graphics/capabilities.jpg" ;
    capabilitiesbuttondown     = new Image() ;
    capabilitiesbuttondown.src = "graphics/capabilitiesover.jpg" ;

    contactsbuttonup       = new Image();
    contactsbuttonup.src   = "graphics/contacts.jpg" ;
    contactsbuttondown     = new Image() ;
    contactsbuttondown.src = "graphics/contactsover.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" );
    }
}