function butt_on(bname){
but = eval(bname + "_1");
document [bname].src = but.src;
}

function butt_off(bname){
but = eval(bname + "_0");
document [bname].src = but.src;
}
	
function SetArrowOn(arrow_name){
	document [arrow_name].src = "_library_img/left_menu_arrow_1.jpg";
}

function SetArrowOff(arrow_name){
	document [arrow_name].src = "_library_img/left_menu_arrow_0.jpg";
}

b1_0 = new Image(); b1_0.src = "_library_img/intro_b1_0.jpg";
b1_1 = new Image(); b1_1.src = "_library_img/intro_b1_1.jpg";
b2_0 = new Image(); b2_0.src = "_library_img/intro_b2_0.jpg";
b2_1 = new Image(); b2_1.src = "_library_img/intro_b2_1.jpg";