As I practice HTML + CSS sometimes, you will need transparent space for columns if it contain images and text inside a table. For example, if you have a one image under a column of first row and second column of the same row contains text, image will not show it's full size. For that, you will need transparent space inside first column according to the width of that image. I am not pro but let me know if I am wrong.

Informative tutorial indeed, btw.