When you cut/paste from your e-mail into Google Sites, you're going to get a white background on your posts that shows up when people view it. Annoyingly, it doesn't show up while you're editing it.
This is because Google "sees" additional information in what was cut from the e-mail and pasted into your post.
You can get rid of this by doing this:
Click Edit post
Highlight the text
Click the color that's the same color as your background color, then click Save
