If you are using Unity, go into your project settings -> Player -> Other settings. If you are set to Color Space of Linear your project will only use WebGL. If you downgrade to Gamma, you can add the WebGL 1.0 under the Graphics APIs (shown in the screenshot) and select the Auo Graphics API which should fix the issue error. However most up to date browsers should support 2.0 except Safari on mac. If they are getting that error on Firefox then most likely they need to update their browser