Internet Exporer 7 Running On Vista In Protected Mode

I have just found the cause of an odd error that has been occurring for certain users of our web application.

A tester was reporting a JavaScript error when clicking on a link to open a new window to an external site. Looking at the script the code looked fine. I tracked the code down to the line reported in the error and found it was falling over on window.open().

After a small amount of research I ended up on the MSDN documentation site and found that apparently for IE7 running in protected mode on Vista (the default setting by all accounts), window.open() may not return a valid reference to the new window. So code that calls
var w = window.open() and then attempts to use w will fail as w will be null.

You can read more here.

Unhelpful is a word that springs to mind.