Here's a tip I discovered kind of by accident in one of those "I wonder if" moments.
It came about after discovering a Fiddler tip that lets you trace localhost http traffic. The solution is simple: you simply add a trailing space, so that you surf to http://localhost./
At first I'd assumed that this was some odd quirk in the way browsers handled host names. Turns out it's actually working the way it should. Technically speaking all FQDNs should have a trailing space, in order to make them absolute. More here.
It's not just localhost. By way of an example the following two links both work
But, what's the tip?
My tip is that you can use the above "hack" to login to (most) websites using two different identities at the same time.
Oftentimes you want to test websites as two different users (even if one of them is "anonymous") and find yourself logging in and out as each user constantly.
Well, using the same browser, you can login as "User 1" at the site with no trailing dot and then as "User 2" in the site with the dot!!
Since discovering this a couple of hours ago it's already saved me an inordinate amount of time.
I know you can always do this by using different browsers (User 1 in Chrome, User 2 in IE) but it's normally the case that using the non-system-default browser ain't so straightforward.