I'm building the homepage part of the website and I need to make a sidebar and an overhead (upper) bar. How do I do it?

**I only want to write a declarion for the whole website so these bars should stay on every page.

See Cascading Style Cheatsheet

Under Box properties look for the CSS "float" property. This property can be used for objects like "div" to create side bars. Test the page in various browsers though, because the wrapping behavior around the sidebar can vary. Look for the "clear" property when something needs to be below the sidebars.

Many people code headers, sidebars and footers as HTML tables. Sometimes using the HTML colspan property (for headers and footers), sometimes nesting a table (for the contents) inside table(s) used for a header and footer. Please set width properties with the colgroup tag so the page doesn't shift around while it is rendering! See the various "table" "tr" "td" , "col" and "colgroup" links at EchoEcho.Com - HTML tag Reference

A convenient method for using a single header and footer for a large number of pages (or an entire site) is to use frames. Separate files for the content, common header, common footer and comon sidebar (usually a navigation menu) are stored on the server. Javascript code attached to the links changes the "location" of the frames using the "name" property to control which frame is changed. Look for "frame" and "frameset" links at EchoEcho.Com - HTML tag Reference