Misconceptions among students studying physics have been widely reported in the research literature. Many teachers are not acquainted with this literature. Moreover, many of them claim that only weak students have misconceptions. This paper reports on an online activity focusing on misconceptions of students regarding Newton's 3rd Law, that is being carried out through the website of the National Center of Physics Teachers. The aims of the activity are: (1) To convince the teachers that sometimes difficulties in understanding concepts do not stem from the inability of certain students to understand the concept, but rather because of misconceptions in physics. (2) To present the teachers with the findings of studies on physics instruction that deal with the concepts under discussion. (3) To convince the teachers to try out new, innovative teaching strategies.