var button_no=0;
var pics=new Array();
function preload(pic_name,pic1,pic2)
	{
	button_no++;
	pics[button_no]=new Array(4);
	pics[button_no][0]=pic_name;
	pics[button_no][1]=new Image();
	pics[button_no][1].src=pic1;
	pics[button_no][2]=new Image();
	pics[button_no][2].src=pic2;
	}
<!--j=1 - картинка(кнопка) не активна; j=2 - картинка(кнопка) активна; j=3 - картинка(кнопка) нажата(вдавлена); -->
function change_pic(pic_name,j)
	{var i;
	for (i=1;i<=button_no;i++)	if (pics[i][0]==pic_name)
	{document.images[pic_name].src=pics[i][j].src;continue;}}

preload('img1','../image/kn.gif','../image/kn_click.gif');
preload('img2','../image/kn.gif','../image/kn_click.gif');
preload('img3','../image/kn.gif','../image/kn_click.gif');
preload('img4','../image/kn.gif','../image/kn_click.gif');
preload('img5','../image/kn.gif','../image/kn_click.gif');
preload('img6','../image/kn.gif','../image/kn_click.gif');
preload('img7','../image/kn.gif','../image/kn_click.gif');
preload('img8','../image/kn.gif','../image/kn_click.gif');
preload('img9','../image/kn.gif','../image/kn_click.gif');
preload('img10','../image/kn.gif','../image/kn_click.gif');
preload('img11','../image/kn.gif','../image/kn_click.gif');
preload('img12','../image/kn.gif','../image/kn_click.gif');
preload('img13','../image/kn.gif','../image/kn_click.gif');
preload('img14','../image/kn.gif','../image/kn_click.gif');
preload('img15','../image/kn.gif','../image/kn_click.gif');
preload('img16','../image/kn.gif','../image/kn_click.gif');
preload('img17','../image/kn.gif','../image/kn_click.gif');
preload('img18','../image/kn.gif','../image/kn_click.gif');
preload('img19','../image/kn.gif','../image/kn_click.gif');
preload('img20','../image/kn.gif','../image/kn_click.gif');
preload('img21','../image/kn.gif','../image/kn_click.gif');
preload('img22','../image/kn.gif','../image/kn_click.gif');
preload('img23','../image/kn.gif','../image/kn_click.gif');
preload('img24','../image/kn.gif','../image/kn_click.gif');
preload('img25','../image/kn.gif','../image/kn_click.gif');
preload('img26','../image/kn.gif','../image/kn_click.gif');
preload('img27','../image/kn.gif','../image/kn_click.gif');
preload('img28','../image/kn.gif','../image/kn_click.gif');
preload('img29','../image/kn.gif','../image/kn_click.gif');