Detect special characters in text box. Or any character you subsitute for the special characters.

var iChars = "!@#$%^&*()+=-[]\\\';,./{}|\":<>?";
for (var i = 0; i < document.formname.fieldname.value.length; i++) {
if (iChars.indexOf(document.formname.fieldname.value.charAt(i)) != -1) {
alert ("The box has special characters. \nThese are not allowed.\n");
return false;
}
}