OK, First don't delete your style.css my website uses a style.css with file over 2 TLOC. 2nd it was invent by the W3C consortium with version 1 appearing in 1996. .less files are dynamic css files that have some extra features like nesting. For your reference lesscss.org en.wikipedia.org/wiki/Cascading_Style_Sheets Code (markup):
I have read this site http://verekia.com/less-css/dont-read-less-css-tutorial-highly-addictive, and i found another style language and one of them using .less file format..)