Websites can be coded to perform better with some browsers rather than others.
Sometimes changing the browser you're using will work better with the sites your having problems with.
That setting is, from within the Browser App, (BBKey > Options > Browser Configuration > Browser Identification).
Changing that to another browser might help your BB interact better with some websites. In combination with all of the other configuration settings, you need to find the combination of all of these settings that works best for the sites you are visiting. Sadly, there is no "best advice" to give as each persons needs are different.