This will work for sites where the text is there in the page on load, but hidden with CSS until some point when JavaScript removes the class doing the hiding - perhaps after an animation has been triggered, or fonts have been loaded, or some other random event you quite possibly don't care about but someone else thought was important (sometimes the so-called "FOUC" or "Flash Of Unstyled Content" is fixed in this way).

However, turning off CSS in order to thwart these sites won't work at all for cases where the actual content itself is pulled in with JavaScript, eg. anything built with Meteor.