Revenue from Ads in Web game is practically dead.
Its not what it used to be.
Most people these days only use it for exposure and marketing.
You should put your twitter handle/website/..etc, hardcoded in your game,
that'll get you some followers and good exposure for your next 'commercial' game.
As for the plot, you can add it into the game before the start of the first scene.
This way, even if the description on the page got re-written, they can't change the real plot in the game.