if (document.images) {
 nav1_home  =new Image();  nav1_home.src="buttons/nav1_home.gif";
 nav1_home_o=new Image();  nav1_home_o.src="buttons/nav1_home_o.gif";

 nav2_drums  =new Image();  nav2_drums.src="buttons/nav2_drums.gif";
 nav2_drums_o=new Image();  nav2_drums_o.src="buttons/nav2_drums_o.gif";
 
 nav3_guitar  =new Image();  nav3_guitar.src="buttons/nav3_guitar.gif";
 nav3_guitar_o=new Image();  nav3_guitar_o.src="buttons/nav3_guitar_o.gif";
 
 nav4_keys  =new Image();  nav4_keys.src="buttons/nav4_keys.gif";
 nav4_keys_o=new Image();  nav4_keys_o.src="buttons/nav4_keys_o.gif";
 
 nav5_inst  =new Image();  nav5_inst.src="buttons/nav5_inst.gif";
 nav5_inst_o=new Image();  nav5_inst_o.src="buttons/nav5_inst_o.gif";
 
 nav6_prod  =new Image();  nav6_prod.src="buttons/nav6_prod.gif";
 nav6_prod_o=new Image();  nav6_prod_o.src="buttons/nav6_prod_o.gif";
 
 nav7_cont  =new Image();  nav7_cont.src="buttons/nav7_cont.gif";
 nav7_cont_o=new Image();  nav7_cont_o.src="buttons/nav7_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+'.src');
}