Like any other online location, I promote it. My official site gets top promoting focus over my other locations [even over Tapastic].
I advertise online through free ad spaces on Project Wonderful, through online communities like #Webcomicchat, organically on my social media profiles for each page update, when I live stream I have a banner with my URL on it, any art event I participate in I include my main site URL, gotta make sure it's everywhere but only where it's called for and not obnoxious like at the end of every comment adding a url lol
Also, link swapping with friends online is another way to cross promote and help each other.
And I advertise offline. I have a 5 page mini comic, with a unique Oops story [not yet shared online] that gives a sample of our comic, a URL to our site, and a contact email address, and we use these as promo freebies and business cards.
I drop off batches of them at comic book stores, take hundreds to comic conventions, libraries, normal book stores, community centers, and wherever they'll let me leave them for the most part. And people LOVE free mini comics. Out of the thousands we've handed out at fairs and conventions, I've never seen one of our mini among the flyer debris littering the floor.
Also after each comic convention we attend, I look for comic book stores in the area and leave any extra minis [if any are left] at the store [with manager permission of course].
So yep, I draw people to our site through a BUNCH of hard work, and hope that it also spreads by word of mouth.