How to remove stains from my bathtub?

I saw some stains on the bathtub and thought it was just some stains that can easily wash away using my shower gel... But it doesn't work! How can I remove the yellowish brown stains on my bathtub? :confused:

Bleach is effectively for stain removal. Put on rubber gloves to prevent bleach from harming your skin. Get yourself a spray bottle and add in required amount of bleach. Spray on the affected area and leave it for awhile. Use sponge to scrub it away.

Have you tried Jif (or is it Cif now?)?

This is critical as some cleaning methods cause damage or even worse staining to certain kinds of tubs.
Ways To Clean Porcelain Tubs:
Use an abrasive powder(Comet or Ajax is a perfect example of this), Use a scouring pad, Clean very tough stains with a pumice stone(his is recommended for tougher stains when scrubbing.)
Ways To Clean Enamel Tubs:
Use commercial cleaners, Try shampoo, For serious stains, apply trisodium phosphates, Avoid bleach and drain cleaners.
Ways To Clean Acrylic Tubs:
Wash your tub often, Use vinegar, Be sure to use soft sponges, Use soft cleaners are the key here, since acrylic is easily scratched, Avoid pumice stones and scouring pads, Avoid waxing.