function addLoadEvent(func){
	var oldonload = window.onload;
	if(typeof window.onload != 'function'){
		window.onload = func;
	} else {
		window.onload = function(){
			oldonload();
			func();
		}
	}
}

function alertTextareas(){
	var textareas = document.getElementsByTagName("textarea");
	for(var i = 0; i < textareas.length; i++){
		textareas[i].onkeydown = function(){
			return doNotWriteMore(this);
		}
		textareas[i].onchange = function(){
			return doNotWriteMore(this);
		}
	}
}

function doNotWriteMore(ta){
	if (ta.value.length > 401){
		ta.value = ta.value.substring(0,400);
	}
}

addLoadEvent(alertTextareas);