I've always wondered~ why do people place stones on top of headstones for?! Thanks!?
I went to a cemetary to put flowers on my grandmother's head stone and saw small piles of stones on some of the grave markers..and it dawned on me ..I don't know why.
According to Rabbi Maurice Lamm (author of "The Jewish Way in Death and Mourning") the custom of placing stones on the monument "probably serves as a reminder of the family's presence. [The evidence that this grave is attended, visited and cared for, is respectful for the deceased - NS]. Also, it may hark back to biblical days when the monument was a heap of stones. Often the elements or roving vandals dispersed them, and so visitors placed other additional stones to assure that the grave was marked."
Also, by placing a stone we further participate in the "construction" of the tombstone -- which in itself constitutes a mitzvah.
Incidentally, it is not a Chabad custom to place stones on tombstones.
What the person above mean't I have no idea,as it is nonsense,
hope this helps explain it.