ie8 var w= window.open() - "Message: Invalid argument."

IE is picky about the window name argument. It doesn't like spaces, dashes, or other punctuation.

This is an old posting but maybe still useful for someone.

I had the same error message. In the end the problem was an invalid name for the second argument, i.e., I had a line like:

   window.open('/somefile.html', 'a window title', 'width=300');

The problem was 'a window title' as it is not valid. It worked fine with the following line:

   window.open('/somefile.html', '', 'width=300');

In fact, reading carefully I realized that Microsoft does not support a name as second argument. When you look at the official documentation page, you see that Microsoft only allows the following arguments, If using that argument at all:

• _blank
• _media
• _parent
• _search
• _self
• _top