Putt først dette scriptet mellom HEAD-taggene:

<script> //verify for netscape/mozilla var isNS4 = (navigator.appName=="Netscape")?1:0; </script>

Her får du ikke skrevet inn spesialtegn, som: @!#$%^&* m.fl.

<form onSubmit="return false;"> <textarea rows=2 cols=20 name=comments onKeypress="if(!isNS4){if ((event.keyCode > 32 && event.keyCode < 48) || (event.keyCode > 57 && event.keyCode < 65) || (event.keyCode > 90 && event.keyCode < 97)) event.returnValue = false;} else {if ((event.which > 32 && event.which < 48) || (event.which > 57 && event.which < 65) || (event.which > 90 && event.which < 97)) return false;}"> </textarea> </form>

Her får du ikke skrevet inn enkle eller doble hermetegn:

<form onSubmit="return false;"> <input type=text name=txtEmail onKeypress="if(!isNS4){if (event.keyCode==34 || event.keyCode==39) event.returnValue = false;}else{if (event.which==34 || event.which==39) return false;}"> </form>

Dette feltet aksepterer bare tall:

<form onSubmit="return false;"> <input type=text name=txtPostalCode onKeypress="if(!isNS4){if(event.keyCode < 45 || event.keyCode > 57) event.returnValue = false;}else{if(event.which < 45 || event.which > 57) returnfalse;}"> </form>