Which as always shows what utter garbage HTML/CSS frameworks are. Nothing like violating separation of presentation from content by pissing all over the markup with presentational classes that should only apply to ONE media target.
HTML is for saying what things are, NOT what they look like... and slopping classes for every possible combination into the stylesheet and the markup is such an utter middle finger to why HTML and CSS even exists, and so utterly reeking of the worst of browser-war's era 1990's practices, you might as well go back to writing all those FONT and CENTER tags, ALIGN and BGCOLOR attributes, and TABLE for layout idiocy you all seem to so clearly and dearly miss!
Bootcrap just continues it's long standing tradition of making everything harder, more complex, and take longer to create; not matter how many BALD FACED LIES to the contrary people yum up because they learned the derpy framework before they knew enough about HTML or CSS to even know if it's any good.
Go find a stick to scrape that off with before you go tracking it all over the Internet's carpets.