14a15,50
>     if (targetPage != "" && !validURL(targetPage))
>         targetPage = "undefined";
>     function validURL(url) {
>         var pos = url.indexOf(".html");
>         if (pos == -1 || pos != url.length - 5)
>             return false;
>         var allowNumber = false;
>         var allowSep = false;
>         var seenDot = false;
>         for (var i = 0; i < url.length - 5; i++) {
>             var ch = url.charAt(i);
>             if ('a' <= ch && ch <= 'z' ||
>                     'A' <= ch && ch <= 'Z' ||
>                     ch == '$' ||
>                     ch == '_') {
>                 allowNumber = true;
>                 allowSep = true;
>             } else if ('0' <= ch && ch <= '9'
>                     || ch == '-') {
>                 if (!allowNumber)
>                      return false;
>             } else if (ch == '/' || ch == '.') {
>                 if (!allowSep)
>                     return false;
>                 allowNumber = false;
>                 allowSep = false;
>                 if (ch == '.')
>                      seenDot = true;
>                 if (ch == '/' && seenDot)
>                      return false;
>             } else {
>                 return false;
>             }
>         }
>         return true;
>     }