If R.S.V.P. is written on an invitation it means the invited guest must tell the host whether or not they plan to attend the party. It does not mean to respond only if you’re coming, and it does not mean respond only if you’re not coming (the expression “regrets only” is reserved for that instance). It means the host needs a definite head count for the planned event, and needs it by the date specified on the invitation.

for further details you can alwayz visit the source link…

http://answers.yahoo.com/question/index;_ylt=AukOufgNSHZbl5ToCxb_KN_CxQt.;_ylv=3?qid=20070916194610AAgR0s1

Seriously, this was just asked an hour ago. You should probably check for your question before asking it over again.