The most important step in creating a free online comic is the comic itself. As free and online as it may be, no one's going to read it if it isn't any good. Come up with an original or captivating idea, and flesh out the characters, themes, and plot development. Work on naming the comic, as well.
Remember that comic books are a visual medium. Begin by creating sketches, and listing physical attributes, of the main characters of your web comic. Physical attributes can accentuate personality traits of the characters, and so are very important.
If drawing by hand, you'll need a pencil and a piece of paper for this step. If you're animating digitally or using web-based comic creation tools, you'll need your computer, Internet connection, and animation software.
In order to load the comic onto a website, the images and text will need to be digitalized. If you're working with computer-based animation, you're already there. If you're animating by hand, you'll need to scan the images onto your computer and save them. If neither of these methods appeal to you, use your favorite search engine to find an online, comic creation tool, and create your images through said tool.
Having a URL, or web address, is essential to creating a free online comic. The URL can be the name of the comic, or the name of its creator. If you plan on starting your own comic site or publication, it's smart that the URL reflect this name.
Design your page to fit the themes and look of your comic. Make sure it's ready to go online by the time you've finished your first few strips, or pages, of comic. Test the page in a browser so that you can fix any potential glitches before going online.
Post your comic online. Unless you've set up some sort of payment system, your website will be free to look at, so you needn't worry about the free part of your online comic. Posting it on your site is the last essential step to creating an online comic book.