You have to have a certain mindset while communicating online. Especially using text-based communication like IRC, ICQ, or Yahoo. Text follows rules like logic and syntax. It's a string of words that follow a preset pattern.
Take a look at this sentence. It makes sense only when you reach the last word. That's how text communicates. Communication in real life takes in whole chunks of information at once and it's not all words. Text can't convey the totality of human communication: facial expressions, nuances, gestures, inflections. Text cant tell you whether the voice is steady with conviction or wavering with uncertainty. We get around that somewhat by using emoticons, but that's like comparing a burp with a symphony.
By using text, we tend to supply the mood. We give spin, meaning, intentions, and motivations that probably werent intended by the sender, but we perceive nevertheless because we supply it ourselves based on whatever state of mind we have at that time. This makes for very innacurate communication.
The proper mindset for using text-based communication is the ability to isolate the words; to take them at face value, suspending judgement. Stick with only the facts presented without imputing meaning and motivation beyond what is written. Recognize the fact that the communication is incomplete and request for more information if the meaning isnt clear. This is easier said than done, especially when communicating with someone who has an emotional involvement with us. We tend to impute meaning to the words typed that arent really there and this results in misunderstanding and defeats the purpose of communication. How do we isolate the text from the person typing them? How do we isolate the text from our own perceptions and biases? We can't. We werent built to communicate with text alone which uses mostly the logical part of our brains. The use of the keyboard itself is farther removed from who we are than, say, using a pen. At least by using a pen, we impart some of our personality in the words we write. Not so the keyboard. The keyboard is disastrous to many a personal relationship unless the parties learn that this is a totally different form of communication with different rules. Learning that could save us from mixed signals and miscommunication.