In IIS (Windows) with SSI support, you might view parsed output via browser, but again, no specific “top” view.
When using percentages, the value is calculated relative to the height of the parent element. For example, if the parent element has a height of 500 pixels and the top property is set to 20%, the top edge of the viewport will be 100 pixels (20% of 500 pixels) from the top of the parent element. view shtml top