Can I use an enameled trivet on the stove top?
I would not recommend using this trivet on any heat source. First, because that is not what it is designed to be used for. Secondly the description says that they have rubber feet, not a good match for a heat source. And while I suppose you could remove them, I couldn't recommend that in good conscience.
EDIT
As per @Jefromi's comment below and as evidenced on  Dictionary.com , there are two types of trivets.

noun
1.a small metal plate with short legs, especially one put under a hot platter or dish to protect a table.
2.a three-footed or three-legged stand or support, especially one of iron placed over a fire to support cooking vessels or the like.

The type shown in the ad/picture in the question is designed to be used to protect table tops and counter tops from the heat of a hot pot or pan.