PCIe 1.0a is the first commercially available PCIe implementation. It was followed up by PCIe 1.1, and then PCIe 2.0, and then PCIe 2.1, and then PCIe 3.0.
PCIe 1.1 is a minor improvement on PCIe 1.0a. It doesn't change anything electrically, so many motherboards that shipped with PCIe 1.0a can be upgraded to PCIe 1.1 through a simple firmware update.
PCIe 1.0a is the first commercially available PCIe implementation. It was followed up by PCIe 1.1, and then PCIe 2.0, and then PCIe 2.1, and then PCIe 3.0.
PCIe 1.1 is a minor improvement on PCIe 1.0a. It doesn't change anything electrically, so many motherboards that shipped with PCIe 1.0a can be upgraded to PCIe 1.1 through a simple firmware update.