This blog article about image compression in C2
is probably an appropriate ressource for you to check.
Let us know if you still have doubts afterward ?
Also the jumpyness you experiment is probably due to the fact that IE9 does not support webGL and thus only renders in canvas as you mentionned.
I suggest you to also install and try chrome and firefox (as secondary browsers) to test your games. You might be surprised in the end by the results.
Also make sure that your graphic card drivers are up to date.