A common practice when writing code is to annotate incomplete or questionable areas with comments prefixed with warnings like TODO, HACK, FIXME, and so on. MonoDevelop draws attention to these by recognizing them and highlighting them.
The Task List pad, accessed from View->Pads->Task List, has section that lists all of these items and allows you to jump directly to them. This is useful if you’re looking for things to fix.
There are several built-in tokens for recognizing task comments, but you can define your own in Preferences->Task List. When you add a task comment token, comments with that token will be highlighted and listed the same way as the built-in ones.
You can also set different importance levels for different task tokens, and can set the colours used in the task list for the different levels.