By default it is 1140px wide, but if the user resizes the browser or access it via a mobile device, it will adapt the size and content to fit in the viewport width.
Based on the 960 Grid System and other famous CSS tools.
Here are some key features of "Columnal":
· Built-in debugging CSS to show the structure of any pages being built
· Sub-columns (columns within columns) for more layout options
· Prefix and suffix for extra space within a column before or after content
· Vertical spacing CSS classes
· PDF of grid system for sketching out site before building
· Wireframing templates
Limitations:
· Columnal is in active development and may be bugs still present in the code.