一、  ie8支持 placeholder 属性

/*  * ie8支持 placeholder 属性  */ $(function(){ 	 if( !('placeholder' in document.createElement('input')) ){	    $('input[placeholder],textarea[placeholder]').each(function(){   		  var that = $(this),   		  text= that.attr('placeholder');   		  if(that.val()===""){   		    that.val(text).addClass('placeholder');   		  }   		  that.focus(function(){   		    if(that.val()===text){   		      that.val("").removeClass('placeholder');   		    }   		  })   		  .blur(function(){   		    if(that.val()===""){   		      that.val(text).addClass('placeholder');   		    }   		  })   		  .closest('form').submit(function(){   		    if(that.val() === text){   		      that.val('');   		        }   		      });   		    });   	  }  })