Changed the examples, added more details about each formatting method, and cleaned up grammar. Also made the text easier to read and comprehend, as well as more attractive.
* Translate challenge subtitles and example challenge text to Spanish
* Corrected errors in syntax and punctuation
* Multiple corrections of it/s to its plus other grammar corrections
* Correction and added paragraph to CSS Flex article
* Corrected my own typo
* Corrected capitalization, American spellings and typos