You are likely to have a strong claim against someone who registers a domain name using your trademark and then uses it to sell similar products. Even if they have some right to the domain name, you could take court action against them for breaching your intellectual property rights.
The position becomes less clear-cut if the website does not relate to the products covered by your trademark. You will still have a strong claim if they are deliberately passing themselves off as being related to your business.
Similarly, you may be able to take action against companies that use your trade mark in their websites: for example, so that an Internet search for your trade mark comes up with their website.
As this is a complex and changing area of law, you should take advice.
