У вашего броузера проблема в совместимости с HTML5
Are you lagging and have a crappy Pc? Well look no further i will teach you how to obtain more frames just by using 2 legal mods.
Links:
Optifine http://optifine.net/downloads
BetterFPS http://minecraftsix.com/betterfps-mod/
Lively Default Pack http://www.minecraftforum.net/forums/mapping-and-modding/resource-packs/2091397-150-000-downloads-1-7-1-8-lively-default-greener
Recommended Settings for Optifine: (These can vary depending on your pc)
Graphics= fast
Smooth Lighting= OFF
Fog= OFF
Render Distance= 4-8 (8 is for custom clouds)
Max Framerate= Unlimited
Use VBOs: ON *(VERY IMPORTANT)*
1st Track: Riant-JJd
2nd Track: Candyland-Tobu
*I DO NOT OWN THESE TRACKS AS THEY ARE FOR ENTERTAINMENT PURPOSES*