select original window

I was having problem while selecting the original window following the closure of popUp window. Error was "com.thoughtworks.selenium.SeleniumException: ERROR: Window does not exist. If this looks like a Selenium bug, make sure to read http://selenium-core.openqa.org/reference.html#openWindow for potential workarounds"

This got resolved when used selenium.selectWindow("null") instead of selenium.selectWindow("name=null") to select the original window.