Help with XML documents and loops?

[Derek275]

It comes up with a message box that says this:
"An unhandled exception of type 'System.NullReferenceException' occurred in Eclipse.exe

Additional information: Object reference not set to an instance of an object."

And then it highlights:

Code:

button.Tag = node.Attributes("URL").InnerText

Any idea? <!-- s:? --><img src="{SMILIES_PATH}/icon_e_confused.gif" alt=":?" title="Confused" /><!-- s:? -->