From Math Teachers at Play:

Analyzing mistakes is a great way to learn. Can your algebra students explain what went wrong in these Algebra 1 Math Mistakes? Can your geometry students make sense of these Geometry Math Mistakes?

From the Math Forum:

Every day since last summer, New York City high school math teacher Michael Pershan has posted a photo of a math error made by a student — and invited other teachers to come analyze and discuss the misunderstandings behind those mistakes.

These two postings represent the dual uses of the site: student and teacher analysis. As we compile more errors, this site is becoming increasingly valuable as a source for student analysis.