I have a field and want to prevent some illegal characters while showing the user as he types. How can I do this in follow example?

  $('input').bind("change keyup", function() {
   var val = $(this).attr("value");
   /*
   if (val --contains-- '"') {
    $(this).css("background", "red");
           val = val.replace('"', "");
              $(this).attr("value", val)
   }
   */
   $("p").html(val);
  });

EDIT: I should put the illegal characters in an array

var vowels = new Array('"', "<", ">", "&");