How to setup a left and right page section? Panels?

How to setup a left and right page section? Panels?

Hi
I have an MVC project that uses a left panel thats fixed, it has buttons and info, it never moves.  On the right, that area is variable and can have charts, images, paragraphs, more charts, and links to data.

Well, the problem is when I use #Left and #Right in the div declaration, and modify the CSS, etc, there will be a left side thats good, right side is Okay until the size is reduced.  Shrink it to the minimum?  there is a Horiz scroll bar on the bottom of the right area.  Move it? and the right side contents flood into the left and mix in and it looks terrible.

The hope is to find some way to start out with a Left and Right panel, about 23% and 77% at full screen and a 35/65 or 40/60 ratio when at the smallest screen width.  I thought if there is a way to just have these panels, and test by coloring them and expanding/shrinking then put in the div's that may work.  Already have far too many hours trying to tweak the fractions of CSS settings where its good at full screen, good at small screen but then the horiz scroll bar, slide it over?  The right side data writes over the left side.  If that right side data would just disappear  and not overwrite the left? it would be ok, but if there is some panel or way to put all of these groups so they will jumble around and auto arrange?  that would be best.  Thanks for any suggestions