Have you tried playing with the settings - turning on Reduce Particles, turn off Post Screen Affects, limit the framerate to 30 frames per second? Also if you are playing on Chrome you are running the WebGL version which for some people doesn't run as well as the Unity Web Player version. Just a heads up the WebGL and Web Player versions save to different locations so you'll need to pair your game before trying a different browser for your save to transfer over.
Have you tried playing with the settings - turning on Reduce Particles, turn off Post Screen Affects, limit the framerate to 30 frames per second? Also if you are playing on Chrome you are running the WebGL version which for some people doesn't run as well as the Unity Web Player version. Just a heads up the WebGL and Web Player versions save to different locations so you'll need to pair your game before trying a different browser for your save to transfer over.