Small Javascript / jQuery project

We need a javascript package that will accomplish keeping a nav bar 'above the fold' regardless of browser window size. The element should work identically to the bar containing the 4 image buttons on [login to view URL] The bar should either stick to the bottom of its container (overlaying the large image) on large windows, or move up to stay visible when the window is smaller than the large image. The script must work identically to the one on laperla, be fully cross browser compatible (including working on ie8+) and work well with other instances of js and jQuery on the same page. The code should be well commented and easily configurable for use in alternate designs.