An illustration of the way row markings can aid in reading the information contained within a table. The markers illustrate the way your eyes behave when trying to move from one column to the next.
Because your eyes have nothing to guide them across the empty space, you will have a hard time trying to match the name of the song with the corresponding artist.
The horizontal lines provide an aid to guide the eye from one column to the other. However, the lines are only one pixel (1px) tall, and following the line from one column to the next requires extra effort to follow the single pixel across the width of the table.
Each stripe provides a guide that’s 17px tall, which makes it much easier for the eye to move from one column of the table.