Several different style sheets can be attached to a document and all of them can influence the presentation of the document. HTML focuses on the structure of a document rather than the appearance. Therefore, CSS is valuable because it puts the designer in control of how the web page will look. Two units are used when using Relative Positioning, em and percentages. TOP is used to specify how far down the element goes from the normal top edge and LEFT to specify how far to move it to the right of its left edge.
Negative values move the element up and left.
The Absolute units are inches, centimeters, points, and pixels. With my experience using both Relative Positioning and Absolute Positioning in CSS, I feel neither one is better than the other. Both have benefits when used in certain situations. Relative position is more beneficial to use on a page where elements are updated or changed frequently. On the other hand, I felt I had more control of the placement of elements when I used Absolute Positioning.