Misuse of English conjunction related to incoherent writing, according to the literature, comes from learners' first language interference, improper mechanical exercises, and misleading lists of connectors in textbooks demonstrated as if mutually interchangeable without contextual constraints. Form-focused instruction with explicit semantic, stylistic and syntactic properties can help learning of connectors. Additionally, computer learner corpus analysis which identifies systematic interlanguage patterns in Chinese learner data offers pedagogical insights for the current study. Four Web-based online conjunction units based on principles from related literature and learner corpus analyses were designed for 19 EFL college students to use for a month with sentence-beyond contexts concerning stylistic properties and overuse situations. Before and after the project, a gap-filling test on conjunctors and a writing task were used, followed by an evaluation questionnaire on students' perception. Results indicated that students generally held a positive attitude toward the online units and demonstrated statistically significant improvements in the use of connectors in both the test and free production contexts. The case study argues that pedagogically sound instructional design for online conjunction materials can help college EFL learners write more accurate and coherent essays. (Contains 4 figures and 4 tables.)