People get damn defensive when you point out a major misspelling or grammar mistake. The grammatically incorrect can become emotional or even violent. I think that’s because you’ve pointed out an obvious mistake that’s visible to the entire world, and they either can’t argue against you because they never knew what they were doing in the first place, or because they know it’s wrong and they can’t talk their way around it. We all make typographical errors, and we all make grammatical mistakes. Some people just make the same mistakes repeatedly and refuse to admit or correct those mistakes when someone else politely points them out. (I, for one, realize I have a problem with “its” and “it’s”, and I’m working on it.)
On the Internet, you are primarily represented by what you write, and when you write badly, it hurts your personal credibility and the credibility of your point. Sometimes mistakes go beyond simple letter transposition and constructive technicalities to the point where mistakes can change the meaning of a sentence, create ambiguity, or make the sentence itself undecipherable. Those instances are much more frequent than you might expect from an allegedly educated populace, and attempting to assist or correct those who build such monstrosities is often a pointless exercise in frustration.
Whether you believe good writing is critical in this primarily written medium or not, you should read Eats, Shoots & Leaves by Lynne Truss. Grammar and punctuation are not unquestionably certain things (spelling is a little more so), but the book provides many good guidelines for being an effective writer and some excellent examples of how bad writing can cause confusion or even calamity. This book isn’t a lecturing tome filled with academic minutiae, rather, it’s a friendly volume with a sense of fun and some very humorous examples. You owe it to yourself and the people you expect to communicate with to read this book and understand why what you write is so important. If you can’t be bothered to take time to clearly make a point, why should anyone be bothered to take you or your point seriously?
And now for my standard disclaimer: I don’t claim to be a perfect writer. I make mistakes too. Crawling my site, parsing every word in every posting, looking for errors is a waste of your time, as I don’t care what you find, and it’s immature, not to mention that if you do so, you obviously didn’t comprehend this posting at all.

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February 1st, 2006 at 2:07 pm
This is a great book.
You will be amazed at the number of errors in grammer people make all the time.
The author is a BIT obsessive about it though.
G