Resizing screen problems

Hi, I’d like some help with an issue I’ve been having when resizing the screen. My sidebars for homepage(front-page with the three widgets) and the other pages seem to shrink when the screen is resized rather than becoming layered one on top of the other.
So for example when I resize my homepage width, the widgets get slimmer and display the text in a long line rather than each homebox being in a different line. Basically all the homeboxes are in the same line even when the screen width is adjusted when they should be appearing one above the other. Hopes this makes sense.

I am using a child theme of the Responsive theme http://wordpress.org/themes/responsive
Please I need your help, deadline is up against me. Thanks