What is the ruling on supervising mixed-gender websites and forums, even though their advantages outweigh their disadvantages?

The positive and negative aspects of your work are not clear to us, and judgment of something is based on its conception. If the work in this forum involves forbidden matters, such as men and women conversing without need or without adhering to Sharia guidelines, then it is not permissible for you to work there, because it entails assisting in sin.