function initPlaceHolders(){
	if('placeholder' in document.createElement('input')){ //如果浏览器原生支持placeholder
		return ;
	}
	function target (e){
		var e=e||window.event;
		return e.target||e.srcElement;
	};
	function _getEmptyHintEl(el){
		var hintEl=el.hintEl;
		return hintEl && g(hintEl);
	};
	function blurFn(e){
		var el=target(e);
		if(!el || el.tagName !='INPUT' && el.tagName !='TEXTAREA') return;//IE下，onfocusin会在div等元素触发 
		var	emptyHintEl=el.__emptyHintEl;
		if(emptyHintEl){
			//clearTimeout(el.__placeholderTimer||0);
			//el.__placeholderTimer=setTimeout(function(){//在360浏览器下，autocomplete会先blur再change
				if(el.value) emptyHintEl.style.display='none';
				else emptyHintEl.style.display='';
			//},600);
		}
	};
	function focusFn(e){
		var el=target(e);
		if(!el || el.tagName !='INPUT' && el.tagName !='TEXTAREA') return;//IE下，onfocusin会在div等元素触发 
		var emptyHintEl=el.__emptyHintEl;
		if(emptyHintEl){
			//clearTimeout(el.__placeholderTimer||0);
			emptyHintEl.style.display='none';
		}
	};
	if(document.addEventListener){//ie
		document.addEventListener('focus',focusFn, true);
		document.addEventListener('blur', blurFn, true);
	}
	else{
		document.attachEvent('onfocusin',focusFn);
		document.attachEvent('onfocusout',blurFn);
	}

	var elss=[document.getElementsByTagName('input'),document.getElementsByTagName('textarea')];
	for(var n=0;n<2;n++){
		var els=elss[n];
		for(var i =0;i<els.length;i++){
			var el=els[i];
			var placeholder=el.getAttribute('placeholder'),
				emptyHintEl=el.__emptyHintEl;
			if(placeholder && !emptyHintEl){
				emptyHintEl=document.createElement('span');
				emptyHintEl.innerHTML=placeholder;
				emptyHintEl.className='placeholder';
				emptyHintEl.onclick=function (el){return function(){try{el.focus();}catch(ex){}}}(el);
				if(el.value) emptyHintEl.style.display='none';
				el.parentNode.insertBefore(emptyHintEl,el);
				el.__emptyHintEl=emptyHintEl;
			}
		}
	}
}