Need answer why my wmlscript is not working. I have made it really
simple and it still doesn't work. simple1.wml has 2 cards. Card 1 asks
user to enter a 4 digit number. GO executes function in simple1.wmls
to check length, then returns to Card 2 in simple1.wml to display
number or ERROR. Files below.

I have configured the webserver with the correct content type mappings:
.wml   text/vnd.wap.wml
.wmls  text/vnd.wap.wmlscript

I have tried on both real phones and with WAP phone emulators
(Wapalizer, WapTiger, etc.). All display the first card of simple1.wml
OK. But when I enter a number and press GO, I get "Services: Reply
unknown" on the phone. Wapalizer gives me the underlying error, which
is HTTP Error 406.

You can access the files hosted at the following URL:
http://ww2.xilo.com/mpos/simple1.wml

WML file (simple1.wml):
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>

<card id="card1" title="Card 1">
<do type="accept" label="GO">
  <go href="simple1.wmls#checknumber($(mynumber))"/>
</do>
<p>
Any 4 digit number: 
<br/>
<input type="text" name="mynumber"/>
</p>
</card>

<card id="card2" title="Card 2">
<p>
Your number: $(mynumber)
</p>
</card>
</wml>

WMLScript file (simple1.wmls):
extern function checknumber(mynumber) {
  if (String.length(mynumber) != 4) {
    WMLBrowser.setVar("mynumber", "ERROR");
  }
  WMLBrowser.go("simple1.wml#card2");
}