With our latest release, you now choose a fixed or fluid layout, to optimise your experience when using Codebase. We recommend using fixed layout which is enabled by default for all new users, but should you wish to use the fluid layout, just head to your profile via the settings:
From here, under Preferences, you can change the Site Layout under the following area:
The following screenshots demonstrate the difference between the two layouts used with a screen resolution of 1920x1080.