How do you remove dark stains from a toilet seat?

I have used Cif (in England) Soft Scrub (in America) or any cleaning agent with grains in that can scrub the stain off. This is the only way. For a more natural cleaner, try a paste of bicarbonate of soda, this may work too, but Soft Scrub definitely did the job when I had to clean the toilets in a house I moved into. This basically scrubs the stain off so if the toilet is colored it may take the color off !