Place this in a your header:

<style>
@media screen yahoo {
  * {
    overflow: visible!important
  }
  .y-overflow-hidden {
    overflow: hidden!important
  }
}
</style>

Yahoo is adding overflow-y: auto to all tags containing a max-height. This causes scrollbars to appear and hides elements using max-height: 0. Setting overflow: visible!important will override this property. If you want a value other than overflow: visible for a particular element, you will need to use a yahoo-specific override class. Eg.<div style="max-height: 300px" class="y-overflow-hidden"></div>