Identifying what type of slot your card fits into
Below are three cards each with one of the 3 different slots your card will fit into:
When the card is on the table with the chips facing up, the metal bracket will be on the left. The bottom tab is a touch over 2 ½" from the metal bracket. The tab will have staggered pins one pin will have a wider top with a thin bottom and the next pin will be the opposite with wider bottom and thin top. Some of these types of cards will have an extra tab that comes down about the 2" area. Some may have the part of the tab that starts around the 5 ½" area, this part may or may not have pins on it. But the main way to identify these cards are the staggered pins on the connector tab.
As with an AGP card the metal bracket will be on the left when the chips are face up. The connector tab starts about 1 ½" from the metal bracket. The pins will all be uniform, some may be missing, this is normal as not all cards need all of the pins to function and the manufacturer left them off. The tab will have a gap at about 4 1/8". These cards can be of any type including video cards.
Unlike the other two cards, the metal bracket will be on the right with the card lying with its chips face up. The tab starts about 1" from the bracket. And has a larger gap than the other two types at 4". This type of connection is the oldest type and are being discontinued on newer motherboards. It is strongly recommended that if you have a video card for this slot, you should upgrade. You will notice a large difference. The pins are all uniform in size and wider than the PCI pins.