<SCRIPT LANGUAGE="JavaScript"> <!-- Begin var mikExp = /[$\\@\\\#%\^\&\*\(\)\[\]\+\_\{\}\`\~\=\|]/; function dodacheck(val) { var strPass = val.value; var strLength = strPass.length; var lchar = val.value.charAt((strLength) - 1); if(lchar.search(mikExp) != -1) { var tst = val.value.substring(0, (strLength) - 1); val.value = tst; } } function doanothercheck(form) { if(form.value.length < 1) { alert("Por favor, entra algún carácter."); return false; } if(form.value.search(mikExp) == -1) { alert("Entrada correcta"); return false; } else { alert("Lo sentimos, pero los caracteres siguientes: \n\r\n\r@ $ % ^ & * # ( ) [ ] \\ { + } ` ~ = | \n\r\n\ no están permitidos.\n"); form.select(); form.focus(); return false; } alert("Entrada correcta"); return false; } // End --> </script>

<form name=xyz onSubmit="return doanothercheck(this.txtTerm);"> <font size="4">(caracteres no permitidos: <i>$@#%^&*()[]+_{}`~=| </i> )</font>:<i><br> </i> <input type="text" name="txtTerm" size="60" maxlength="50" value="" onKeyUp="javascript:dodacheck(xyz.txtTerm);"> <br><br> <input type=submit value=Comprobar> </form>