The :last-of-type selector matches every element.
The reason for this is that every time a new element is added to the DOM, it is checked to see if it matches one of the CSS selectors. Because the DOM is build one element at a time, every element is at least once the last element of a certain type.
The selector should only match elements that are *really* the last of a certain type. Once an element is no longer the last of a certain type, it should no longer match the :last-of-type selector.
*** This bug has been marked as a duplicate of 5468 ***