I’m sorry but it is beyond the scope of these forums to deal with general CSS issues. Try a dedicated CSS resource such as http://www.css-discuss.org/ instead. In the meantime, using Firefox with the Firebug add-on for this kind of CSS work. Or use whatever developer tool is available in your web browser.
http://getfirebug.com/
And remember to validate your CSS & markup.
is there any good reason why you have edited the css classes of the sidebar div?
also, you seem to be using fixed widths in the styles – this is probably not useful in a responsive, i.e. flexible, theme.
Usually, when I see the sidebar area “jump” to the bottom of the page (especially during custom development)… it is almost always an unclosed <div> tag somewhere in the code.
Use firebug to check your code.. and make sure all div tags are properly closed.