Sounds like a driver issue.
Add a textbox and set it's content to "renderer" (without the qutation marks). If implemented correctly, it will output the default renderer currently employed by your browser (either WebGL or, worst case scenario, Canvas).
It would also help if you could add your computer's specs to the original post and either upload or describe the game you're trying to run (e. g. does it use physics? Total/approximate amount of objects on screen? Custom behaviour, pathfinding, etc?)