Primary & Secondary widths not working responsive

Hello, First thank you for making available such a wonderful theme. Catch Box is very elegant. My question is this: I changed the Primary & Secondary widths to 660 and 250 respectively but when I resize the window to a tablet or phone size the primary section doesn't resize anymore. I made sure the sizes add up to 910px as in the original but my resizing seem not to work when in responsive mode. I used:

#primary {width: 660px;}
#secondary {width: 250px;}

How can I fix that please? Thank you once again.