I need help with creating a donation confirmation page

Hello,

I have create a website for our new non-profit organization. Everything is ready to go except when someone makes a donation this is the confirmation page they are sent to. It's a black page until you run a mouse over it and highlight the text. Not good. I have created a thank you page but for the life of me, I can't access this black page to change the background color nor the text. 

Can someone please help?? We planned to launch our website today and just learned about this glitch last eve.

Thank you for responding. The problem is I can't find the confirmation page in order to edit it. The only way I can even see the confirmation page is if I make a donation and there is no edit capability on the confirmation page.  

I was able to access and change the theme that was causing the issue. Thanks so much!

Glad to know that it is fixed now.