[Full Question: What is the ruling for promoting websites for products (such as those for weight loss) which may have pictures on their site of women in indecent clothes, like bikinis, for example? Is it forbidden to direct people to these products/sites?]
When a businessperson has the right to choose what to promote and what to avoid, (if he is the owner of the company, for instance, not an employee), it is required that he not promote such websites.
However, we need to note that these websites are not intended to promote pornography, obscene literature, or even immorality, and that not all of their content is half-naked women. That is why promoting them is definitely not as prohibited as promoting pornographic or other obscene websites.