Optimizing Sluggish UI


I’m new to Vaadin, and i’m working on the optimisation and the amelioration of our company application (it’s a huge vaadin 6 software).

Our client is complaining about the slugglish application when using IE11. So from your following article

I’m using customLayout instead of panels. So if i put a Layout : vertical or horizontal layout in a customLayout is it better than putting them in a panel?
What is the best way of using the CustomLayout API to optimize the different UI?

Kind regards,