This is for a debug app (programming) that prints additional information when the mouse is over a certain element.
For example, the app can display a list of class methods. When the user mouse over a method additional information is shown inside a tooltip, like the DocBlock comments for that method.
Currently I'm using CSS and javascript to display the tooltip relative to the mouse cursor position, but I was wondering if it would be a better idea to make it fixed. So when the mouse is over an element, the tooltip will always show in the same place (for example above the element). One advantage of the latter is that it can be implemented with just CSS. But that's less important if it takes away from user experience :)