A huge pet peeve of mine is the use of incorrect typographic marks. The one I see the most if the use of Feet and Inch marks in place of quotation (inverted commas) and apostrophe marks. There are double and single quotation marks and the general rule is that they are shaped in some sort of curve.
The Key on a Keyboard typically next to the return key accesses the feet and inch marks in a given font. However, most word setting applications such as word, indesign and QuarkXPress can be set to override this setting. Displaying the correct quotation marks while you are typing.
What really bothers me about this is that large design firms who get paid a lot of money to create ad campaigns still use feet and inch marks in their posters that are created for their clients. This is simply a huge mistake or they use interns to execute the artwork.