if (document.images) {

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 product_overviewoff = new Image();
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 cryogenic_valveson = new Image();
 cryogenic_valveson.src = "/images/menu_cryogenic_valves_on.gif";

 cryogenic_valvesoff = new Image();
 cryogenic_valvesoff.src = "/images/menu_cryogenic_valves_off.gif";

 vacuum_valveson = new Image();
 vacuum_valveson.src = "/images/menu_vacuum_valves_on.gif";

 vacuum_valvesoff = new Image();
 vacuum_valvesoff.src = "/images/menu_vacuum_valves_off.gif";

 cryogenic_bayonetson = new Image();
 cryogenic_bayonetson.src = "/images/menu_cryogenic_bayonets_on.gif";

 cryogenic_bayonetsoff = new Image();
 cryogenic_bayonetsoff.src = "/images/menu_cryogenic_bayonets_off.gif";

 vapor_ventson = new Image();
 vapor_ventson.src = "/images/menu_vapor_vents_on.gif";

 vapor_ventsoff = new Image();
 vapor_ventsoff.src = "/images/menu_vapor_vents_off.gif";

 specialty_productson = new Image();
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 specialty_productsoff = new Image();
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 }