Google calendar embedded disappears on Edits

I don’t know if this is a but, but I have a page with a google calendar embedded in it. It looks great, etc. But when I go to edit that page, if I’m not careful and click from the “html” tab to “visual” and back, Bang! the embedded calendar code disappears. So, I have to go back and resize etc and input it again. So, now I’ve saved the embedded calendar code for whenever I play with that page, I can retrieve the settings quickly.

Thanks