There's thousands, millions of article sites out there. You might even count blogs as article web sites and there are new ones popping up every day. The question is: what writing makes you want to read them?
You. You you you.
You. It's all about you. When writing an article or a tutorial, make sure it's directed to the person reading it. No one cares about what the author thinks, you want to get the job done. You don't care about them. Make sure you don't use words like “we, us, I” and use “you.” It keeps the article or tutorial personal.
Keep the grammar casual, but still good. Do you want to sift through a mess of spelling errors and run-on sentences trying to figure out what the author is saying? No, of course you don't. No one does. Spell check it, grammar check it, read over it once. Make sure your readers can understand you.
When you read an article, usually you want to see some kind of concrete proof about something the author is talking about. If the article you're reading is a tutorial, you want to see the end result, right? So put it at the beginning. You don't want to have to scroll all the way down to see what the final outcome of all your work is to decide you don't like it. Put your examples at the top to show your readers.
Keep It Casual
Make sure your readers aren't bored. If you're going to be writing a long article, might as well make it fun for them to read. You don't want to read an article straight from a science journal (unless it is a science journal), and even then it should still be somewhat casual. I've seen some science articles that are interesting because of how it's written.
Put a spin on your writing. Make it your own. It's cliche, yes, but do it! No one wants to read the same idea over and over. I know I've been somewhat guilty of it, but some rule breaking is allright. Like talking about myself here. It's an example. Refer to #3.
Bold words always help. So do lists, links, and quotes. Readers like you can skim for the bold words they're looking for, and find what they want. It's perfect for them. Saves time, and gets to the point.
Always have an awesome conclusion that wraps it up nicely. You always want to see that whole work of art brought together with a nice summation. So if they want to skip that boring article you wrote because they didn't pay attention, you can hope they'll read that nice summarized conclusion. Like this: Make the article personal, use lots of examples and styled text to make the article easier for the user, watch your grammar, and make the article your own and have fun with it!