Responsive css help please

Let's say I have 2 divs that I want to be aside. Either with float:left,either with display:inline-block.
The div with id #div1 I want to be responsive with max-width:700px and the div with #div2, I want o have standard width. Let's say 200px.
I want when the user decreases the size of the browser, the left div (#div1), to minimize it's width, WITHOUT sending the right div (#div2) under.
I want the right div, to be under, only when REALLY dont fits in the screen.
And the left div, to behave just like it is alone. To really decrease it's width.
Is is possible ??? If yes, HOW ????
I dont use and css framework.

An example here:http://archipelago-lng.eu/Results/Publications.html

The left div (the one with the right border), and the right div-column.
Right now, i'm changing the left div's width, with media queries.
But, i want to behave just as when it's alone. (minimize it enough), to see that the red border really decreases...

Thanks in advance

I wrote about this a few months back: http://ronaldroe.com/solving-common-design-problems-using-css-calc/

The 4th use case is the one you're needing.

Ronalroe !
Thank you very much!!!!
That's exactly what i was looking for, and it works!!!(refresh my link, if you wanna check),

I will check if it works in chrome, opera, safari and ie (the damned...)
I hope it works for ie 9 and above...

I just used the width:calc() and it worked as a charm!

Thanks again, and have a happy new year!