Custom thank you message with graphic

I can't seem to be able to customize the "thank-you" message for a submission. I get to the screen to change it, it either won't let me type a message or when I finally get to, it won't let me format it. What am doing wrong?

Hello vdarlene,

I am not able to replicate the issue you are having. I edited your form and was able to format the custom thank you message without any problem. Please check the screenshot below:

It could be temporary browser related glitch and clearing your browser cache should solve your problem. The following guide should help you:  http://www.wikihow.com/Clear-Your-Browser's-Cache

Do get back to us if the issue persists.

Thank you!