From Section 5.50 of the
OP2 Processing Manual:
Internet relationships
An Internet relationship alone, without other convincing evidence that the couple has established and maintained a conjugal relationship for at least one year and spent time together, will raise serious concerns as to whether a conjugal relationship exists. Conjugality should be assessed based on the elements of interdependency as set out in Section 5.26 above.
Yes, it's absolutely okay to say you met online . . . in fact, you don't want to be dishonest or misleading about how you met. And there's no need to apologize for meeting online! So be honest. The bottom line is that how you met is not nearly as important as what happened after you met. (This section seems also to assume an application as conjugal partners, rather than spousal or common-law where a relationship is established in law or by the fact of having cohabitated for at least one year.) What's most important in assessing a genuine and continuing relationship (meaning not just about facilitating status in Canada for the foreign national) is your ability to document and evidence a
history that supports it. We met online, as have many, many others, and there was no question about our genuine and continuing relationship because we were able to demonstrate that after the initial "meet", we traveled frequently to spend time together and talked daily by phone, etc. And we had pictures, cards, receipts, trip itineraries, etc., to support that. This section of the manuals is talking about relationships where people have not only met online, but have maintained the relationship strictly online . . . that would be a really easy thing to do if someone was looking only to immigrate to Canada - if CIC allowed it. They don't.