CSS problem

H folks,

I want to do a sheet with alternate colored lines.
IE, first line red, second line green and so on.

But:
..grn {
   border-style: solid;
   border-widht: 2px;
   border-color: red;
       }

..rot {
   border-style: dotted;
   border-widht: 2px;
   border-color: red;
       }

wouldn´t work with:

<p class="grn">Line 1</p>
<p class="rot">Line 2</p>
<p class="grn">Line 3</p>
<p class="rot">Line 4</p>


So what´s wrong?
Thanks in advance

John