UPDATE (21/8/2010): I have come across one URL string that didn’t match this, only one. Maybe they are phasing this out, will keep you posted if I find out.

So you’re checking out someone’s profile image on Twitter and you click the image but only to be greeted by the login page before you’re allowed to see it in a larger size (If it is any larger that is). Well there is a way to see the larger image without logging in due to the simplistic naming conventions that Twitter has given them 8-) .


Depending on your browser:
Firefox – ‘Right Click’ the profile image and press ‘View Image’ to open in a new page.
IE8 – ‘Right Click’ then go to ‘Properties’ and get the link from ‘Address: (URL)’, copy and paste it into your browser address bar.
Chrome – ‘Right Click’ and press ‘Open image in a new tab’

The URL in your address bar will look something like:
http://a1.twimg.com/profile_images/729784400/fb_profPic_bigger.jpg

Remove the word ‘_bigger’ (and the preceding underscore) and press ‘Enter’:
http://a1.twimg.com/profile_images/729784400/fb_profPic.jpg

Boom!

NOTE: I’ve also seen the word ‘_normal’ used, does the same thing though.