Hi Oleksiy,
Try inserting a call to the Refresh method in your code before the call to the FindChild method. Also, try using "NativeWebObject.id" (for Internet Explorer) or "NativeFirefoxObject.id" (for Firefox) instead of "idStr" as the value of the first argument of the FindChild method. If this does not help, please provide us with a script that demonstrates the problem with a public site.
As for your note, native Firefox objects contain the getAttribute method, but as the enumerator returned by the getElementsByTagName method has a different structure in Firefox and Internet Explorer, it is necessary to access the enumerator's elements using the different approaches you've mentioned.
