My blog was all messed up today on some browsers. So I e-mailed Blogger support. I received a fast and helpful response from Graham. Thanks Blogger!
So you at home don't make the same mistake, here's what Graham wrote.
In a recent post, you'll notice that you typed a long series of
dot-dot-dot- etc. Unfortunately, a browser doesn't interpret these hyphens
as break points for wrapping lines to fit in the window, so it puts it all
on one line. This stretches the width of the rest of the content along
with it, so your whole blog becomes too wide. You can fix it by cutting
down that list of dots, or by adding some spaces in it.
I hope that helps.