make floating widgets cut off before blocking content

hi,
i know there are media queries that change a sites layout etc. at particular sizes.
But what if want to simply remove widgets sooner to prevent blocking of content ?

http://ecochemex.com/exhibitor-list/

the floating widgets on the left and right is blocking content on some users screens.
Looks great on my screen but i gather they may have smaller screens and when i drag my browser i can see where it blocks the content a bit before it goes away completely.

Is there a way to make these floating widgets go away sooner without interfering with the media queries or layout of the entire site ?

Any kind assistance in this would be greatly appreciated.

RC.