如何让divs适应动态屏幕分辨率？

I need to have 3 divs, out of which 1 is set to width of 1000px and be in the middle of the page, and the other 2 should fill the screen width from the left and right of the main div. I want this to work on all screen resolutions but I can't find the way to do it.I need to have 3 divs, out of which 1 is set to