LESS is a dynamic style sheet language. LESS provides the following mechanisms: variables, nesting, mixins, operators and functions; the main difference between other CSS precompilers being that it allows real-time compilation via LESS.js by the browser. LESS can run on the client-side and server-side, or can be compiled into plain CSS.
When you upload your .LESS file to your account, but it does not load and gives you 404 error, please add MIME type "text/css" for .less file from your hosting control panel-->IIS manager -->mimemap
if need more info about Mime type configuration, please check the below link.