HMTL code doesnt show on the admin page?

Hello,

I am doing some updates for a non profit company and I am having difficulties as I am unable to see the html code for some of the pages… when I am in the control panel and I choose the page I would like to update, there are pages that show only two words, and the rest blank, then there other pages that show only 10 lines of html coding but nothing else. I was wondering what could be causing this, if anyone could help me it would be mean a lot as I have to finish this for next week. Thank you kindly.
Egg