This study intends to shed light on the most occurring grammatical and lexical (pragmatic) errors which students make in their compositions. For this purpose, 23 male and female undergraduate students from different majors were asked to take part in the present study. Each week, for four weeks, students were asked to write 4 compositions on predetermined topics. Students' writings were analyzed for errors based on a linguistic Category Taxonomy and the frequency of errors for each category was calculated. Two kinds of corrective feedback were devised based on the type of errors observed, deductive (explicit) explanation of interlingual errors and inductive (implicit) clarification of intralingual errors. After the treatment, students wrote four more compositions and the frequencies of errors for the two sets of writings were compared to see if any significant changes had occurred. It was found that the most errors were of interlingual category (71%). It was also concluded that in 22 out of 26 categories, the frequency of errors decreased. Deductive (explicit) teaching of interlingual and also inductive (implicit) teaching of intralingual erroneous points decreased the error frequency of students. Moreover, interlingual errors were more affected than intralingual in case of error reduction.