I am having a problem on handling the pop up windows in robot framework. 
The process I want to automate is :
When the button is clicked, the popup window appears. When the link from that popup window is clicked, the popup window is closed automatically and go back to the main page. 
While the popup window appears, the main page is disabled, and it can be enabled only when the link from the pop up window is clicked.
The problem I have here is that I cannot go back to the main page after clicking the link from the popup window. I got the following error.
20140604 16:04:24.160 :  FAIL : NoSuchWindowException: Message: u'Unable to get browser'
I hope you guys can help me solve this problem.
Thank you!
I have seen this issue and found that there is a recovery period where Selenium does not work correctly for a short time after closing a window. Try using a fixed delay or poll with Wait Until Keyword Succeeds combined with a keyword from Selenium2Library.
Going back to the main page after closing the pop up window