Why are there series of elements at the bottom of the Periodic Table?
The elements at the bottom of the periodic table are in group 3 following Lanthanum and Actinium respectively. Those element were moved to the bottom of the table to allow it to be in a format that could be printed. Click here to see the Periodic table with those elements inserted.

Why are there two group numbers for each of the groups?
The periodic has multiple number formats for numbering the vertical groups. The Americans and the Europeans both have different systems for numbering. The tables in this site use the American system which has the numbers and letters. Also these tables have a single number at the top of each column. This method is a compromise proposed by the International Union of Pure and Applied Chemistry (IUPAC).

Why do some elements not have names? Why do some Periodic Tables have different names for the elements?
There is some controversy over the naming elements above 92. Due to several groups being involved with the discovery of some of the newer elements it is not clear who should be able to name some of the elements. Also, there is an element named for a living scientist which is traditionally not done