I like my English to be written correctly. Spoken English can be, and usually is, a lot less formal and I am as guilty as most of all the usual bad usage. I was brought up to believe English should be written properly. Along with most lessons at school however, I did not pay particularly good attention during English. So this site listing most of the common errors in English could be a huge help.
My spelling is not brilliant either, so I have a tendency to copy my blog entries to Microsoft Word to spell-check them before I publish them.