The header and footer of an oscommerce based store needs to be changed based on the _root page of site. All links must be made so as to have sids and should work without errors. You can either copy the css based header n footer of current site or make it in tables (ofcourse using css for common width, colour etc). It should also appear ok in major browsers.
And the root page of the site is required to look the same in IE7 as in other browsers. The site is currently compatible in FF2, Opera9, Safari and IE6, so please see it doesn't break compatibility with these. Site layout is CSS based and XHTML. After your changes both CSS and XHTML must remain W3 validated.
Coding must be simple and clean. Nothing sort of a big task. Budget is below $20.