when we submit to SEs, should we submit a single site only or submit multiple pages?

another question:
to submit a site, should we submit, i.e.
mydomain.com or www.mydomain.com or www.mydomain.com/index.html?

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SEs typically only require/want a domain submitted once. Your full, primary URL should be just fine (i.e. http://www.domain.com or http://domain.com).