Common issue and it should be a sticky for new members here. The default setting is wrong and needs reset for you to post. First go to your profile up in toolbar above and click. This will open a window on the first screen on your profile editing. You don't want this screen though but you want to click on the personal options on the top in this screen. Once in the personal options screen scroll down towards the bottom and you'll see Editor Type and they're be two choices click on the HTML choice and then scroll down and click on Update Profile and you should then be good to go here.
Respect Our Outdoor Recreational Resources Leaving Only "Footprints in the Sand"