Before starting, I owe you an apology. This week, we released the Developer Preview of Internet Explorer 5. The values are absolute. You can vary any of these properties with script.
Dynamic properties allow any property to be set to an expression.
Note that circular references are not allowed. If there is a circular dependency, all properties in the circularity will not be calculated. On the bright side, circularity detection is done at the property level, so it's possible for element A's width to be dependent on element B's height, and B's top to be dependent on A's left. Dynamic properties can be applied in two ways. There is a new method on every element, and on the style object that can be set in script.