The SarcMark, which looks like a period with a little curl surrounding it, is meant to be used at the end of a sentence in the same way as one might use an exclamation mark to denote excitement, or a question mark to denote a question.
The SarcMark comes in two forms: the font version (which will only be visible to other users who have downloaded the SarcMark), and the image version (which will be visible to all). The image version can be inserted into any text document by hitting the Ctrl + the period key, while the font version can be inserted by hitting the Windows key + the period key. The SarcMark is compatible with Mac OS X (for the font version, you can hit the command key + the period key; the image version is still the Ctrl key + the period key), and various BlackBerries. The company is currently working to make it available on other mobile platforms, such as the iPhone.
The SarcMark can be downloaded for only $1.99. That might seem like a lot to pay for a period on steroids, but think about it this way: You’ll never again have to worry about someone taking a sarcastic remark you made literally. Of course, part of the point of sarcasm is its subtlety…but that’s hard to do on the Internet.
Of course, if you’re cheap, you can stick to denoting sarcasm the regular way (c’mon, SarcMark, did you really think people hadn’t developed some kind of way to denote sarcasm on the Internet?): with emoticons, asterisks, and </sarcasm> tags.