if (document.images) { 

var img17on = new Image();
img17on.src = "../images/cat_nature02.gif"; 
var img17off = new Image();
img17off.src = "../images/cat_nature01.gif";

var img18on = new Image();
img18on.src = "../images/cat_geography02.gif"; 
var img18off = new Image();
img18off.src = "../images/cat_geography01.gif";

var img19on = new Image();
img19on.src = "../images/cat_plant02.gif";
var img19off = new Image();
img19off.src = "../images/cat_plant01.gif";

var img20on = new Image();
img20on.src = "../images/cat_animal02.gif";
var img20off = new Image();
img20off.src = "../images/cat_animal01.gif";

var img21on = new Image();
img21on.src = "../images/cat_insect02.gif";
var img21off = new Image();
img21off.src = "../images/cat_insect01.gif";

var img22on = new Image();
img22on.src = "../images/cat_fish02.gif";
var img22off = new Image();
img22off.src = "../images/cat_fish01.gif";

var img23on = new Image();
img23on.src = "../images/cat_bird02.gif";
var img23off = new Image();
img23off.src = "../images/cat_bird01.gif";

var img24on = new Image();
img24on.src = "../images/cat_human02.gif";
var img24off = new Image();
img24off.src = "../images/cat_human01.gif";

var img25on = new Image();
img25on.src = "../images/cat_fiction02.gif";
var img25off = new Image();
img25off.src = "../images/cat_fiction01.gif";

var img26on = new Image();
img26on.src = "../images/cat_tool02.gif";
var img26off = new Image();
img26off.src = "../images/cat_tool01.gif";

var img27on = new Image();
img27on.src = "../images/cat_vehicle02.gif"; 
var img27off = new Image();
img27off.src = "../images/cat_vehicle01.gif";

var img28on = new Image();
img28on.src = "../images/cat_letter02.gif"; 
var img28off = new Image();
img28off.src = "../images/cat_letter01.gif";

} 


function On(name) { 

if (document.images) { 
document.images[name].src = eval(name + 'on.src'); 
} 

} 


function Off(name) { 

if (document.images) { 
document.images[name].src = eval(name + 'off.src'); 
} 

}