The Custom Markup pane is a relatively simple pane type designed to add custom HTML markup to your page. In its simplest form, this will generate a basic block with some text and a call to action link, if the field is filled in (see image below). This pane might be helpful if you want to add a simple block of text between other panes on your page.
In its most complex form, the Custom Markup pane can be used to generate valid HTML elements. This is done by clicking the Source button on the Abstract field's editor panel. Since this can result in a number of unintended side effects, we recommend getting in touch with ITS (email@example.com) if you are interested in using the Custom Markup pane to create truly custom HTML markup.