Leave the window open, it expires when you close it. Use another browser window to check your mail, or check your mail on a different web browser (like Internet Explorer) or use a smart phone or other device. In most browsers, control-N will open a new window, and control-T will open a new tab (command-N or command-T on Macs.)
Once you get logged in, if you go to your personal settings and add a cell phone number, you can change your security preferences to send any future verification codes to your phone by text message instead of email, if that is easier for you.
