The .sass file has "+column(!main_content_width)" -- what does it mean?

Is it actually part of BluePrint? W开发者_运维知识库hat do they do?

+column(!main_content_width)
+clearfix

Where can some intro docs be found for it? thanks.

These are part of Compass, the stylesheet authoring framework built on top of Sass. See the following:

• http://compass-style.org/docs/reference/blueprint/grid/#mixin-column
• http://compass-style.org/docs/reference/compass/utilities/general/clearfix/

The column mixin is part of the Blueprint module, which is included with Compass.