jquery html5 实现placeholder 兼容password ie6

//判断浏览器是否支持 placeholder属性  
	function isPlaceholder(){  
   	 var input = document.createElement('input');  
    	return 'placeholder' in input;  
	}  
 //对不支持placeholder的浏览器处理
  	 if(!isPlaceholder()){  
            $("input").not("input[type='password']").each(//把input绑定事件 排除password框  
                function(){  
                    if($(this).val()=="" && $(this).attr("placeholder")!=""){  
                        $(this).val($(this).attr("placeholder"));  
                        $(this).focus(function(){  
                            if($(this).val()==$(this).attr("placeholder")) $(this).val("");  
                        });  
                        $(this).blur(function(){  
                            if($(this).val()=="") $(this).val($(this).attr("placeholder"));  
                        });  
                    }  
            });  
            //对password框的特殊处理1.创建一个text框 2获取焦点和失去焦点的时候切换  
            var pwdField    = $("input[type=password]");  
            var pwdVal      = pwdField.attr('placeholder');
            pwdField.after('<input id="pwdPlaceholder" type="text" value='+pwdVal+' autocomplete="off" />');  
            var pwdPlaceholder = $('#pwdPlaceholder');  
            pwdPlaceholder.show();  
            pwdField.hide();  
              
            pwdPlaceholder.focus(function(){  
                pwdPlaceholder.hide();  
                pwdField.show();  
                pwdField.focus();  
            });  
              
            pwdField.blur(function(){  
                if(pwdField.val() == '') {  
                    pwdPlaceholder.show();  
                    pwdField.hide();  
                }  
            });  
              
        }