IE quirk for js window.open

window.open is a common javascript call used to open a new browser window from the current page. The syntax is the following:

var newWin = window.open(url, name, options);

So this should be a perfect call:

var newWin = window.open('http://www.google.com', 'search.page', '');

But it fails with an "invalid argument" error in IE6. The problem is the '.' character in the name parameter. It seems like IE 6 accepts only letters, numbers and '_' for that parameter, but I couldn't find ANY more info about this. Does anyone have more clues about this??