// check browser
function isBrowser_(/* String */nm)/* Boolean */ {
	var mj = parseInt(navigator.appVersion);
	var ua = navigator.userAgent.toLowerCase();
	var op = (ua.indexOf("opera")!=-1);
	var op2= (ua.indexOf("opera 2")!=-1||ua.indexOf("opera/2")!=-1);
	var op3= (ua.indexOf("opera 3")!=-1||ua.indexOf("opera/3")!=-1);
	var op4= (ua.indexOf("opera 4")!=-1||ua.indexOf("opera/4")!=-1);
	var op5p = (op&&!op2&&!op3&&!op4);
	var ie = ((ua.indexOf("msie")!=-1)&&(ua.indexOf("opera")==-1));
	var ie3 = (ie&&(mj<4));
	var ie4 = (ie&&(mj==4)&&(ua.indexOf("msie 4")!=-1));
	var ie5 = (ie&&(mj==4)&&(ua.indexOf("msie 5.0")!=-1));
	var ie55p = (ie&&!ie3&&!ie4&&!ie5);
	var nn = ((ua.indexOf("mozilla")!=-1)&&(ua.indexOf("msie")==-1)&&(ua.indexOf("opera")==-1));
	return eval(nm);
}

// add event for target element.
function addEvent_(/* Element */elem, /* String */event, /* function */func, /* Boolean */b) {
	if(isBrowser_("ie")) {
		elem.attachEvent("on" + event, func);
	}
	else if(isBrowser_("nn")) {
		elem.addEventListener(event, func, b);
	}
	else {
		elem.addEventListener(event, func, b);
	}
}

// remove event for target element.
function removeEvent_(/* Element */elem, /* String */event, /* function */func) {
	if(isBrowser_("ie")) {
		elem.detachEvent("on" + event, func);
	}
	else if(isBrowser_("nn")) {
		elem.removeEventListener(event, func);
	}
	else {
		elem.removeEventListener(event, func);
	}
}