How do i keep a throw rug in place as it's walked on.?

You need a better quality rug pad. Or the one that you have might be dirty, and therefore it cannot adhere well to the floor.

http://www.homedecorators.com/rugPads.php

If the rubber mat is sliding off the rug then try double-sticky taping the mat to the rug. If it is still sliding after thet then you could carpet tape it to your floor, but it will likely leave a sticky mess on your floor. You could also "paint" a coat of water-based elastomeric on the back. It is a latex acrylic roof coating sold at Home Depot as "snow coat" and Benjamin Moore paint stores.

There is rug padding made for this purpose to keep the area rug is place and prevent slipping. Some are reversible to be used on either carpet or bare floors make sure that you are using one that is appropriate for bare floors if you are using your rug on bare floors. This type will have extra grip and will not stain or damage your floor. Hope this helps you out.

spectacular question. My house is in part carpet and in part linoleum. She consistently barfs on the carpet.. yet oh it gets greater suitable. She barfs on my pillow, mattress, and if I ensue to leave clothing out on the floor... yep they get barfed on. it is so stressful!!!!!!!!!!!!!! i can't count selection what share situations i've got had to whip out the carpet purifier after a barf episode. UGH

Carpet tape from a local carpet store.

have you tried double sided tape?

screw it to the wall