To delete a category
Select the category you wish to delete and click the 'Delete selected' link. This will delete only the selected category. If you have selected a category that has a child category, you will not be able to delete this category until you remove the child category.
The tree size 'bigger' and 'smaller' buttons simply allow you to elongate the category tree area. (It only changes the way it is displayed, but makes no actual changes.)
