Bookmarklet to open a new window forwards current window to [Object Window]?

I am using a small bookmarklet which opens a webpage in a new window. It works properly on chrome.

However, when I use the same in Firefox it opens a new window with new web page but the page on which this bookmarklet was clicked is forwarded to some page with text [object Window]. How do I solve this issue?

My code:

<a href="javascript:open('http://www.google.com','targetname','height=500,width=500');">Bookmarklet</a>

Please let me know how to solve this issue.

Thanks