Update frame_bottom.erb

Updated frame_bottom.erb  to have an example of an iFrame  within the /frames URI.   Please modify to suite the usage.  I am only making a suggestion here that is testable by a Selenium script by having a hyperlink that opens a new window.

Keep in mind that if a Selenium script actually clicks the link to open the new window, the browser instance will end up having an array of 7 windows I think:   default, left, right, middle, bottom, iframe, and new_window.  Is this correct?