if (document.images) {
 nav1_home_l=new Image();  nav1_home_l.src="images/nav1_home_l.gif";
 nav1_home_o=new Image();  nav1_home_o.src="images/nav1_home_o.gif";

 nav2_abou_l=new Image();  nav2_abou_l.src="images/nav2_abou_l.gif";
 nav2_abou_o=new Image();  nav2_abou_o.src="images/nav2_abou_o.gif";
 
 nav3_proc_l=new Image();  nav3_proc_l.src="images/nav3_proc_l.gif";
 nav3_proc_o=new Image();  nav3_proc_o.src="images/nav3_proc_o.gif";
 
 nav4_port_l=new Image();  nav4_port_l.src="images/nav4_port_l.gif";
 nav4_port_o=new Image();  nav4_port_o.src="images/nav4_port_o.gif";
 
 nav5_quot_l=new Image();  nav5_quot_l.src="images/nav5_quot_l.gif";
 nav5_quot_o=new Image();  nav5_quot_o.src="images/nav5_quot_o.gif";
 
 nav6_cont_l=new Image();  nav6_cont_l.src="images/nav6_cont_l.gif";
 nav6_cont_o=new Image();  nav6_cont_o.src="images/nav6_cont_o.gif";
}

function btn_over(btn) { 
 if (document.images) eval('document.'+btn+'.src='+btn+'_o.src');
}
function btn_out(btn) {
 if (document.images) eval('document.'+btn+'.src='+btn+'_l.src');
}