It's been a while since I've discussed webcomics theory. Let's give it a try.
Humor is a tricky subject. Most webcomic creators feel that they have to include humor in their strip because that's what the reader expects. The word comic itself suggests a sort of humor. A person that's new to the world of webcomics would only have seen newspaper funnies before. They will grow to expect that sort of humor.
However, there is the danger that if you write a newspaper style strip, noone will want to read it because they already have the newspapers. It's safer to read newspaper strips, too because those people are working for money and are professionals, so of course they'll be better quality (in theory, not practice).
I personally don't think a comic strip needs to be humorous to be read. I actually think that sometimes humor can ruin a strip rather than help it. In webcomics especially, there needs to be a balance between story and humor. Both are aspects of writing used to provide interest to your audience. If you write the same as everyone else, noone will be interested. (and for those who say they are writing for themselves, you know it's not true. I have actively written for myself many times before, but I still responded to feedback. I was still hurt when people didn't like what I'd created. The very fact that you are placing the comic on the interenet means that you want people to see it, and even if you don't realize it, you are subconsciously affected by other people's opinions, even if the reaction is to go against their advice.) However, there needs to be some humor. Even the most serious dramas have some humor. The audience needs a break every once in a while. It just isn't as important as some people tend to think it is.
One of the large problems with writing about humor is that there are so many different styles, and many people tend to fall into just a few categories for kinds of humor they like. As you can probably see by the reading list, I have many tastes when it comes to humor. Even so, I tend to gravitate toward wordplay, especially those shameless bad puns, dark humor, and banter. Banter being a series of really small jokes told rapidly in order to give a mmuch larger effect, or talking in a different way or with a definite rhythm that sounds humorous. (e.g. alliteration, streams of rhyming words, phonetic word associations) for a good example of this, listen to A Prairie Home Companion
(really, it's free), which actually features examples of wordplay and dark humor as well. I also enjoy purposefully faulty logic, which doesn't work unless people know you're being stupid on purpose. A step down from that, I enjoy non-sequiturs, situational humor, satire, irony and some slapstick, as long as it's good slapstick. Saturday Night Live and Mad T.V. do not have good slapstick. After that, it's kind of hit and miss whether or not I will like it.
The point is, humor differs from person to person. There is no joke that will make everyone laugh. Humor is culturally defined. It's personally defined. It's intellectually defined. It's defined by experience. Whenever you put a joke in a webcomic, you run the risk of people not getting it, or getting it, but not thinking it's funny. The best thing to do to appeal to the widest audience is to support your humor with something else that's good; whether it be great story, strong characters, or good art. It's very rare for a comic that focuses purely on humor to be good. Of course, some people would disagree with me on that.
However, I do feel that humor is important within a strip. Even the most serious dramas, if they're good, have a little humor to release the tension. Read Shakespeare. Even in King Lear, or Hamlet there are humorous scenes. There's a reason Shakespeare is still read today. How many other writers from the Renaissance do you know?
So humor is important. It releases tension. It adds a small level of realism. It endears the audience to certain characters. It even helps with catharsis a bit. Humor if used right can be very effective.
How do you write effective humor? That's hard, but there are a few things which I think might help.
Don't rely on one joke to carry the strip. Think about having multiple related punchlines, or a long flow of jokes rather than just one joke when everything else is build-up. Have you ever seen a stand-up comedian perform? A good one, I mean? They often tell long and involved stories that are meant to build up to one huge laugh at the end. However, they don't just have the one huge laugh by itself. Sprinkled throughout the story they use a bunch of smaller laughs to keep the audience interested as well as warm them up for the huge punchline at the end. Also, if the huge punchline fails, there's a better chance everyone in the audience will have laughed at one of the smaller jokes that led up to it.
Also, jokes have a compound effect (not sure if I used the right word there). That is, a series of jokes told in succession has a better effect than those same jokes told separately. I'll discuss that in a little more detail when I review Perry Bible Fellowship later.
Don't be afraid to have jokes or humor which people might miss. It's okay too add subtle humor, obscure references, or humorous moments or dialogue that takes place in the background or partially hidden. Even if most people miss the humor, if you have enough readers someone will catch it, and will mention it to other readers who will go back, notice it, and think the comic is that much better. Think about it, if you get enough people to read your comic, that's great. If you get enough to re-read the comic, your page-views will shoot through the roof. Try to shoot for those re-reads.
Don't try to please everyone with your humor. It's impossible. On the other side, it might be good if you have the resources to ask a few people you trust whether or not they find your jokes funny, especially if you are running a humor concentration comic. It's hard to be completely objective with your own work. Who knows, your collaborator might have a joke or suggestion that you like more than what you have now.
As always, my biggest suggestion is to draw inspiration from other sources. Read. A lot. Try to figure out what works and what doesn't for you because a humor style that you don't find funny probably won't translate when you try to emulate it. I'm not suggesting you steal from people outright. That's illegal, but you can always take lessons from those who came before you. You can also read to find ideas that don't work and avoid those.
Finally, if you're having trouble with your humor, you might want to make a comic that focuses more on characters or story. One thing that's great about webcomics is the different comics don't have to stand alone, and they don't have to be funny to be read. There are many serious and semi-serious comics on my reading list. I think it's the same for most people who read webcomics. Find a style that works. That's really what's most important.
Humor is important, but it's not as important as some people think it is. As with all tools of writing it needs to be used effectively in order to have a positive impact on the audience. Sometimes the way to have effective humor is to use it sparingly. Humor is a small aspect of webcomics writing and should not overpower the overall experience.