I\'m making use of the following code:
.c-1:first-child, .c-2:first-child, .c-1:nth-child(4n+1) { margin-left: 0; }
which is working great but
Maybe check out the following article:
http://abouthalf.com/2011/07/06/poor-mans-nth-child-selector-for-ie-7-and-8/
But the described solution works only in ie7 and 8, in ie6 it won't unfortunately