-e: webplayer builds throw an error when trying to use for example System.IO. WebGL doesn't and then you just get exceptions at runtime

-repro:
--open attached project
--open App_UtilityMethods.cs
--go to WriteBytesToFile defintion
--comment out the #ifdefs so the non-webplayer block is active be default
--try to build for webplayer
--notice it fails with the compiler error
--switch platform to webgl
--build
--NOTICE build succeeds
--run
--click the Take Screenshot button
--NOTICE exceptions being thrown