In general we use no-js while we are designing a responsive web site the format will come like this:
Initially i thought no js means there is no need of java script, funny, it makes no sense. But the actual meaning of no-js tag is, there will be a jquery file called modernizr.js. In modernizr 'e' is not there.<html lang="en" class="no-js">
When the time of modernizr js runs in the program, then it will remove the no-js tag, and replace it as js means java script. It is simple way to know that in our c s s whether or not js is enabled.