What's this error

[mattlanta]

[#20310] Your secure key, used to verify you are posting the topic, did not match the one submitted. Please go back, reload the form, and try again.

I tried reloading and trying again like it asks but it still brings me to that message. It's no big deal though I was just posting a simple comment in the Lounge, and I just wanted to know why this popped up. Never happened to me before. Thanks.