Brown water stain in toilet bowl

[Iestyn]

A brown stain has suddenly appeared at the back of the toilet bowl. I assume it is a water stain but the water from the cistern is perfectly clean and there is no staining anywhere else.
Any ideas as to how I can stop the stain re-appearing?

[plumbbob]

Generally the mark is caused by rust. Either something inside the cistern is going rusty and the water is marking the pan or some piece of iron has come into contact with the bowl and is rusting.

[Jame]

Use plumber help , view in local area best plumber and get help.

[Leo1981]

I had the same problem with my toilet, tryed cleaning but had no luck, couldnt be bothered messing around with it so just bought a new one.

[Myra Hush]

Try cleaning with vinegar to remove stains.

[Philston]

Find a product with a diluted hydrochloric acid, get some rubber gloves and scrub your toilet using a nylon bristle brush.. and be careful

[JustinBarley]

You can use a mix of vinegar (white) and baking soda.
Make it a paste like mix and use it to scrub the stains out. Works great for me.