3. Visiting the HIVST-online webpage: The aforementioned videos can be accessed via this webpage. (i) Besides, it will contain a description of the project, knowledge and benefit of the HIVST, contact of the project team (phone, social media, and email), and information about HIV that promotes perceived susceptibility and perceived severity (constructs of the HBM). (ii) A discussion forum will be created to contain positive feedbacks of previous HIVST-online users (e.g. process evaluation of the previous RCT project), and those given by users of the proposed project. These testimonials provide cue to action (a construct of the Health Belief Model) and create a new subjective norm (a construct of the Theory of Planned Behavior) supporting the use of HIVST-online. As an incentive, a lucky draw will be made to those who leave encouraging comments to this forum. (iii) Participants and project team will add 'LIKE' or further comments to the webpage. (iv) Participants may post their questions in private, which will be answered by the project staff.