Several box model tests here:

.A {  
  margin: 10px 10px 10px 10px;
  border: 10px solid red;
  padding: 10px 10px 10px 10px;
  background-color: blue;
  color: white;
}

.B {  
  margin: 10px 10px 10px 10px;
  border: 10px solid red;
  padding: 10px 0px 10px 0px;
  background-color: yellow;
  color: black;
}

.C {  
  margin: 10px 10px 10px 10px;
  border: 10px solid red;
  padding: 0px 0px 0px 0px;
  background-color: yellow;
  color: black;
}

Note how the horizontal margins do not collapse (20px between elements)

I am an "A" SPAN I am a "B" SPAN I am a "C" SPAN

Now, for a special trick:

Same SPANs, this time inside a table.

I am an "A" SPAN I am a "B" SPAN I am a "C" SPAN