For administrators and power users, it’s often useful to log in as multiple users on the same web site. However, you can’t normally do this from one web browser – sites keep track of your whole session. Logging in as one user logs you out as the other user.
An obvious, but bulky, solution is to use one web browser for each log in (e.g. Firefox and Chrome). However, I’ve found that Google Chrome’s “incognito” feature works much better.
Although incognito was created to provide an untracked, private browsing session, it achieves this by separating itself from the other browsing sessions. So you can be logged into the same site twice: once in the regular browser window and once in the incognito window.
The only caveat I’ve found is that you don’t want to do too much work in incognito. It does not save your browsing history, so you won’t be able to return to previous work once you’ve closed the window.