Each house has its own set of rules. When in question, contact the house and ask. A quick phone call might be the easiest and fastest way to get the information. When you get the receptionist, just say something like this, "Your guidelines say you only accept published authors' submissions. I need to know if online sales count towards publication credits. Could you please direct me to the correct person to answer this question?"
If the receptionist knows the answer, she can give it to you right then, and if not, she will immediately know who to connect you with that can answer your question -- or at least someone who will know who to contact to answer the question. LOL! BEWARE! You MIGHT end up talking to an editor! Be SURE to have your questions and a "sound bite" of your current story written out ahead of time, so that you don't babble and blubber and sound like a total idiot if you do get ahold of an editor. :x <been there, done that!>
And for those who don't know what it is, a "sound bite" is a very tight synopsis of your story or article. It's like the blurb of a story you read on a jacket cover to see if you want to read a book or not when you first pick it up. I recommend writing a "sound bite" of no more than 15 or 20 words for your story. That way, you can pitch it to an editor in one quick sentence.
When writing a sound bite you will give almost NO details of the story. Names don't matter,(except in the case of a biography, like with my book example below) relationships between characters don't matter, (unless that's the whole point of the story -- like if a girl fights with her brother to avoid losing herself in drugs,) all the plot points of the story are left out except the one main one. The only thing you tell is the "heart" of the story -- the main "idea" behind the story.
Examples: If you wanted to write a sound bite for the children's classic story of "The Three Little Pigs," you could say, "A big, bad wolf tries to eat three little pigs by blowing down their homes." For the Harry Potter series, you could say something like this, "A young boy battles a most evil warlock while attending school to learn the craft of sorcery." In my newest book, "Rough, Tough Charley," I would say this, "In my non-ficiton biography of Charley Parkhurst, a runaway orphan becomes a celebrated stagecoach driver, then gives the world a huge surprise when he dies." (The sound bite is the part beginning with "a runaway orphan.")
Hope this helps a little....