quick function to find which selectors aren't being used.

unusedcss.js

function each(items,fn){[].forEach.call(items,fn)}

each(document.styleSheets, function(sheet){
  each(sheet.cssRules, function(r){
    try{
      // look for the first matching element
      if(!document.querySelectorAll(r.selectorText)[0])
        console.log("Unused Selector: ", r.selectorText);

    } catch (e){
      console.log('unable to process', r.selectorText, e)
    }
  })
})