Changing sticky header position as you scroll down

You'll need some sort of javascript to measure scroll position, and than do something based on that scroll position. It could be as simple as setting CSS classes at certain scroll positions an than let the CSS do something with that class.

Couple plugin options depending on what you want to do

Here's some options for doing things with scroll

http://www.webdesignerdepot.com/2013/12/25-free-scrolling-plugins-for-awesome-experiences/

Depends on what you're doing exactly, check out headroom.js. I've used before to shrink instead of hide the header. Fairly easy edit in css.

Hope this helps.

You can definitely use headroom.js for your header. Instead of collapsing it move it up by those 40px. The nice thing is that headroom uses css for the transitions, so change it to move up a bit instead of hiding it completely.

It will look something like this:

.headroom--pinned {
    transform: translateY(0%);
}
.headroom--unpinned {
    transform: translateY(-40px);
}

Thanks guys!