Columns:

1) rs number
2) chromsome
3) position (hg17 build, NCBI Build35)
4) '0' allele in the HapMap phased data. Alleles in the phased data are coded as 0 or 1. All the SNPs were polarized to the forward strand. So the alleles should reflect that.
5) Ancestral allele (chimp allele from pantro2)