How many times have you written something on a forum, blog post, email list or whatever only to find out that somebody took something you said personally when you only meant it in a humorous or honestly offhand manner?
I know I've had the problem many times and if you've been around the Internet more than a few days then it's probably happened to you as well. It's because text isn't as expressive as voices or face to face meetings.
Before you say it, I am not a hamster, I DO know about "smilies" and the fact that they're supposed to help fix the situation. I also know about the "emoticons" that they were derived from, little text codes that were supposed to help substitute for facial expressions and attitude.
The problem with these things is that too many people either don't understand what they mean or they don't use them. I quit using things like that a long time ago because of the fact that they're not really effective. Yeah, I use 'em once in a while on forums, but honestly, mostly it's because I like the look of the little blue one with the sunglasses.
I think that perhaps a better idea would be to use tags similar to html code. For example, you could start a portion of something with: <sarcasm> and when you're done with that part of what you're writing, you would put a </sarcasm> tag.
Things like <joke></joke> tags or <laughing at myself></laughing at myself> or how about <laughing with you not at you></laughing with you not at you>?
I realize that it'd be a pain to type these out but it wouldn't be a problem to keep a list of them in a text file and use copy & paste to put them in when they're needed.
The idea here is that when writing something it's important to make sure that you are very clear in expressing what you MEAN and stop to think about what people will THINK YOU MEAN.
Remember that no matter how funny you think something is, somebody will take it seriously and / or in the altogether worst possible way unless you are clear about your meanings. That is going to mean taking an extra step or two to make sure there are obvious indicators of what you're talking about.
Not just obvious to you, but obvious to anyone who isn't riding around inside your thoughts.