As developer tools are used extensively by front-end developers, it's nice to hint readers that this guide also contains information about developer tools of browsers such as chrome, firefox and edge.
* 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