function load_buttons(){
	var buttons = document.getElementsByTagName("img");
	for(i=0; i<buttons.length; i++){

		if(buttons[i].className=="button_nav"){
			buttons[i].onmouseover = function(){ if(this.src.indexOf("_o.gif") == -1){ this.src = this.src.replace(".gif","_o.gif"); }else{ this.src = this.src.replace("_o.gif",".gif"); } };
			buttons[i].onmouseout = function(){ if(this.src.indexOf("_o.gif") == -1){ this.src = this.src.replace(".gif","_o.gif"); }else{ this.src = this.src.replace("_o.gif",".gif"); } };
		}
	}
}