You can switch back and forth between the windows:
- In Windows, hold down the Alt key and tap the Tab key (called Alt-Tabbing).
You can also use the Task Bar, usually at the bottom of the screen.
- On the Macintosh, click the icon in the upper-right corner to select from a list of currently active applications.
When you are finished with the second site, you can close that browser window without affecting the first window.