The Main Links are the principal navigation in your website to other "pages" and arguable the most important part of your site. Depending on your layout they can appear in different places; some are horizontal and under the header, some are vertical and above the teasers, others are at the very top of the page, and some are split into horizontal and vertical groups.
The links can be split into two groups in the KarmaCMS main preferences by inserting the dashed line, "---". When they are split they are controlled by main links group 1 and main links group 2. The dashed line isn't inserted by default so all links are in group 1 unless you change that.
In every situation the main links are a variable height so a height should never be placed on them. Anything under this div should be able to move down naturally as the main links expand. Usually it is the flexible nature of the main links that throws designers not experienced with dynamic design for a loop.