I took the quiz based entirely on the single image presented, and not visiting the site itself or doing much investigating. Managed to get 8/10 primarily based on the familiar buttons/navbar. Strangely though, after the quiz I was told:
I think it would actually be really interesting to see which sites solicited the most visits and which were judged solely by the image presented. Perhaps that would show some gradations between "obviously bootstrap" and "obviously not bootstrap."
Application Error
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1. Buttons and their rollover styles.
2. Text inputs. In particular, the inset gradient, border radius, and on focus styles.
3. Use of a grid. Obviously many people use grids, but a grid in combo with #1 or #2 is a giveaway.
Definitely the buttons - if you go with bootstrap if it has that bootstrap gradient button, and not if it doesn't you should get 8/10 correct, I think?
I would double check but the server currently gives
"Application Error
An error occurred in the application and your page could not be served. Please try again in a few moments.
"
According to this, Tray.io (Site 3 of 10) was NOT built with bootstrap. However the class names on the form controls and buttons beg to differ - http://tray.io/login/
I'm less likely to trust a site called 'bootstrap hero' if they can't correctly identify bootstrap.
Our site (https://circleci.com) is built with bootstrap, and we've managed to make it feel very not-bootstrapy, with some small font changes and not using the black topbar. The only real clue is the font-awesome/glyphicon logos.
The three columns are pretty characteristic of bootstrap, if you're really trying to look different. The site looks good, so don't take that as a suggestion to do anything differently.
If there were buttons visible, I could usually determine if it was a bootstrap site or not. Next, I would look for a top navigation banner and try to decide from that. If I wasn't convinced by those two, then always picking not-bootstrap worked out well.
Fixed, not sure if I just suck at marking these correctly, they changed layouts (I've been collecting links for a while) or that I've lost the ability to read a class='span12' when I see it.
"12 of 10 sites identified correctly"