For some reason, a <br /> tag has been added to each of the css import lines. You can remove those tags, then save, close and re-open your page. The green lines should be gone, although it makes no difference to your page if they're there or not. They are a Dreamweaver code 'grammar' hint feature, and show when Dreamweaver spots what it thinks may be questionable code formatting.
The page-shifts are normal for mozilla (Firefox) browsers, and happen when you switch from a short page that doesn't need a scrollbar to a longer page that does. This is normal behaviour.
There is a link on this page that may help with the scrollbar issue.