Cox-2 primer for PCR - method how to search good cDNA in Pubmed (Nov/08/2007 )

I want to design primer for human Cox-2 for q PCR. I went to pubmed and search for human Cox-2 cDNA and copy that cDNA sequence to invitrogen for possible primers. the problem of doing this is there are many possibilities and I don't know which one is the best. There are many cDNA listed in Pubmed and how can I know which one is the best?
Do you think we need to search for the DNA mapping? Besides Invitrogen is there any other free website that helps to design primer?

Thanks for help

Hi,

I have always used the most recent sequences when designing primers and have never had a problem (Usually the accession numbers that start with NM_xxxxxx). I use Primer3 to design primers if I'm feeling lazy Again - have never had a problem with that either
Clare