*There's an interesting case to be made that this - not even free access or flash animations or anything else - is the big difference between traditional comics and webcomics. Scott McCloud, in Reinventing Comics (sequel to the excellent Understanding Comics) argues that internet-based comics will have a host of advantages over conventual paper-based ones: they have none of the space limitations of conventional paper, they can include visual effects not possible in print, they can take advantage of the internet's abilities to create branching plots, and so forth. But in the nine years since publication, essentially none of that came off. Most webcomics creators - even the professional ones - don't have the time to create more than one plot, or fill out more than one conventional strip worth of artwork, or add anything more programmatically intricate than a .gif file.
What was different - and the fact that this was missed is kind of surprising, since it's a property of the medium of webcomics itself, not any one comic in particular - was that internet archiving means that any individual comic is available to anyone at any time. Print comics can't do this: if you pick up your newspaper one morning and haven't read the funnies a three weeks, you still want to be able to laugh at Garfield's antics; so everything - plot, setting, characterization, even the jokes themselves - has to be as broadly set out and as static as possible. Even relatively story-based comics (such as Doonesbury) tend to simply throw the cast in various situations and let the jokes fend for themselves**.
The webcomics paradigm is different. Readers can come and go as they choose, but - thanks to the miracles of archiving - they never have to miss a strip. Indeed, most webcomics creators take advantage of this to get rid of all the "Gilligan's Island" plotting and endless recapping that plagues print comics. Instead, webcomics can be highly decompressed, and have long-running story arcs and much larger, better-developed casts, albeit at the cost of making reading all the back archives necessary, even for established readers, and making the front-end comics absolutely incomprehensible to new readers. Fortunately, these new readers can simply trawl through the backstory, although with some of the longer-running comics starting to approach 10 years of 7-comics-a-week updating, this can become a daunting task. Not all webcomics do this (the excellent xkcd comes to mind as a well-made gag-a-day strip) but many do, and, even without showy visuals or funky web effects, it opens up vast new storytelling areas long denied to comics. Probably the best example of this is Narbonic, which is a couple of years long and changes a great deal in the process: you can see the creator realizing she doesn't need to make every strip funny on its own, right in front of your eyes, and it improves greatly for it.
So check out Narbonic and see what I'm talking about. It's a good read.
**Although, if you really really want the backissues of Doonesbury, they're here. Just increment the url.
