Your Guide to Private Browsing
When running a browser in private mode, everything you do is kept separate from your main session, including download lists, caches, browser history, forms, passwords and other temporary files. When the window is closed, all this information is erased, and can't be pulled back up in either a normal browser window nor a new private one. Beyond the obvious advantages -- there's a reason the feature has been dubbed "porn mode" -- having a separate browser that scrubs itself clean has a number of benefits. On a shared home PC, it's perfect for covering your tracks while Christmas or engagement ring shopping. If a paranoid guest needs to hop on your computer quickly, set them up with a private session, allowing them to browse to their heart's content. This produces headache-free perusals of bank balances or e-mail correspondence, prohibiting passwords from being automatically saved.
This trick obviously works in reverse, too. If you have to use a friend's PC or a public computer (such as in a college computer lab or a library), open a private browsing window to help keep your data safe.
Even if no one else touches your PC, having a standalone browser session comes in handy. One of our favorite tricks is to use an Incognito Chrome window to log into multiple accounts on a single service. For example, if you have two Twitter accounts, you can log in to one in your main browser window and the other in Incognito or InPrivate, optimizing your tweeting time.
Yet, these modes are not completely isolated from your main browser. Unlike simply opening a new window, private browsing modes are a completely separate "session" (meaning the two browser windows don't share data back and forth, e.g. you can't drag tabs between them) but they're still based on the primary browser. So your history, bookmarks and saved form data are still accessible from the private mode -- convenient for quickly browsing on the sly, but it means anyone using Incognito on your PC will be able to see just how much time you spend perusing Tumblr.
If you've got some secret browsing to do (we won't judge), here's how to quickly access the feature in the major browsers:
Internet Explorer InPrivate
InPrivate can be opened by pressing Ctrl+Shift+P or by selecting "InPrivate Browsing" from the "Tools" menu. If you don't see the menu, press Alt to reveal it.
Firefox Private Browsing
A private browsing window can be launched with either the shortcut Ctrl+Shift+P or by selecting "Start Private Browsing" from the "Tools" drop down in the menu bar.
You can open an Incognito window by either using the keyboard shortcut Ctrl+Shift+N or by selecting "New Incognito Window" from the wrench menu in the upper right hand corner. (Mac users may find this option under "File" in the menu bar.)
Safari Private Browsing
To launch Safari's private mode you'll need to click on "Safari" in the menu bar and select "Private Browsing..."
Opera allows you to open either a private tab or window (the rest are all separate windows). You can right click on the new tab icon and select "New Private Tab" from the context menu. New private windows can be launched with the keyboard shortcut Ctrl+Shift+N. You'll also find both options in the "Tabs and Windows" section of the Opera menu (the giant red "O" in the upper left-hand corner).