NCBI primer blast problem - (Aug/15/2010 )

The result of my sequencing showed that my primers did not amplify the target but amplified something else please could you tell me how I can work on the ncbi blast to find out what the primers amplified and why?I blasted the sequence but the probleem is that it matches to the vector as it contains more than 1000 bp.Any idea how to do just let me know?

Use the primer design (primer-blast) site on the NCBI website and put the primer sequences in the "use my own primer" boxes.