Find the pattern please

If 1A and 2A = each other... and 1B == 2B and so forth... what is the pattern?

A = hprofile-ak-snc4/157668_1199723770_502865554_n.jpg
A = hphotos-snc7/423799_2713965487230_1199723770_32406866_1122807433_n.jpg


B = hprofile-ak-snc4/173654_1125270601_472808878_n.jpg
B = hphotos-snc6/163306_1982929169298_1125270601_32165628_252365147_n.jpg

C = hprofile-ak-snc4/369601_1395985929_1027615013_n.jpg
C = hphotos-ash4/385406_3007793359285_1395985929_33252367_2064903148_n.jpg

D = hprofile-ak-snc4/173986_1824013308_215598562_n.jpg
D = hphotos-snc7/432087_2431821854625_1824013308_1476878_1869568503_n.jpg