How to restict users from entering special characters in Microsoft Dynamics CRM 4.0

From here: http://a33ik.blogspot.com/2009/09/how-to-restict-users-from-entering.html

Solution is very simple - just add following script to OnLoad event handler of form:

function SwitchOnCheck(ElementId)
{
   var element = document.getElementById(ElementId);
   if (element != null)
       element.attachEvent("onkeyup", function()
{
   var mikExp = /[$\\@\\\#%\^\&\*\(\)\[\]\+\_\{\}\`\~\=\|]/;
   var strPass = element.value;
   if (strPass == null)
       return;
   var strLength = strPass.length;
   var lchar = element.value.charAt(strLength - 1);
   while(lchar.search(mikExp) != -1)
   {
       strPass = strPass.substring(0, strLength - 1);
       if (strPass.length == 0)
           break;
       strLength = strPass.length;
       lchar = strPass.charAt(strLength - 1);
      }

   element.value = strPass;
});       
}