I'm not 100% sure how to articulate this. I have a div on a page sidebar. it is underneath a menu. the div CLASS is .ad-container Some pages have a short menu list and other pages have a long menu list. As you scroll down the page and the .ad-container reaches 100px from the top of the browser screen I want it to have a position of fixed so it is always in the same place as you scroll down. Also, as you scroll back up, when it reaches its original position, the fixed position no longer applies.