Don't worry about a contract when there is no contract

I’ve heard that the publication process can allow for the author to promote his/her own work—I’m curious where ‘promotion’ ends and ‘potential contract violation’ begins. Specifically, what are the limitations for an unpublished author who is ready to start submitting to agents, but has had no contact with an agent yet?

Can an unpublished author submit his/her stuff (following the agent’s guidelines precisely, of course) and additionally refer the agent to a website/blog to see more about that submission if they wish, during the review period?

I’m worried that a referral like this: ‘…Please visit xyz.com, where I have provided you with samples of other material/artwork/resources relevant to the completion of this manuscript…’ would actually be read as this: ‘…Please visit xyz.com, where I will single-handedly void any claim to have never-been-published, by posting my entire manuscript!’

Are such sites/blogs irrelevant, and avoided by agents? Or are they helpful?

I think this question refers to what is commonly known as 'putting the cart before the horse'. Where there is no contract, the author cannot be in violation of one. Thus, an author who promotes his or her own work on a website when submitting to agents or publishers cannot be in violation of any contract and, in fact, is more likely to be looked on favourably because he or she already has a web presence.

What that author shouldn't do is direct the agent or publisher to the web for the submission itself. I.e. do not say, 'Dear agent, instead of sending you a proper submission I'd like you to go to my website.' That just looks lazy. And you know what I think about lazy authors? PASS.