I am using GUI miner to mine on Slush's Pool. I have connected with my miner and everything is connected. I have even had a share accepted. But it says my worker is offline. Why is this?
A GPU miner does not have sufficient speed to satisfy the minimum difficulty requirements of pooled mining today (which is why it shows as offline). GPUs have been completely obsoleted since 2013, this is unlikely to change for the better, even if you find valid shares you will have spent several orders of magnitude more in power than it is worth.