"God's is the Earth and all on it" is a translation of the first verse of psalm 24, which in Hebrew is L'Adonai ha'aretz oo'melo'ah

L'Adonai : To God
ha'aretz : The land, the ground, the Earth
oo'melo'ah : from the root word to fill, literally "and that which fills it"

When an observant Jew buys something, he or she should be aware that they don't really own it. Rather, all property is supposed to be a loan from God.

Some people have taken to writing the phrase "L'Adonai ha'aretz oo'melo'ah", or an acronym of it (expressed as lamed-hei-vav), on things they own, especially on the sorts of things that normally have name labels on them.

Books are a typical example. Religious books look very similar, and in study sessions many people might all be using the same book. It's quite normal to write "This book belongs to David", or whoever, on the front page. Often, if you look closely, you'll see lamed-hei-vav in the corner.

While generally this is resticted to things like books, I have once seen it on a house, in Safed, under its name-plaque.

This is only a custom, not a Jewish law. It's quite a sweet one, though.