ok let me try explain you situation.
I have for example 6 widgets in sidebar:
1. -posts widget
2. -ads widget
3. -posts widgets
4. -ads widget
5. -posts widget
6. -ads widget
This ads are variable sizes 300×600 – 300×250 – 300×70
Whet i set this 2 & 4 & 6 – ads widget to be fixed, when you scroll page widget 2 get sticky than when widget 4 get sticky and widget 6 never get in screen if this ads are 300×600 both, or one 300×600 and second 300×250 what is most cases…
In situation when this will be sticky at bottom when you start to scroll page, widget 2 will stick at bottom, and when widget 4 come in screen it will push this widget 2 up and when last widget 6 come in screen also will push 2 & 4 up and in that case this case all 3 will be visible in screen for some time (deepening on screen size and scrolling directions)
Thanks for your time.
Regards!