If you tried to bleach your tub whiter but it came out looking like a murder scene, DON'T PANIC! You can fix it for about $1.50 and no elbow grease.
I recently moved into an apartment in Berkeley. It's a nice big place, but kind of a fixer-upper, with a fair amount of cleaning to do.
One of the problem areas was the bathtub: it looked a bit dingy, with vague yellow streaks down the sides. So I bought some bleach, rubbed it on thick, and let it sit for a couple of hours.
When I came back, my bathtub looked like a scene from a horror movie. Literally: rusty red-brown streaks all down the sides and bottom like dried bloodstains. Exactly how I imagine it would look if you murdered someone in there.
Naturally, I freaked out, turned on the shower, and started scrubbing- to no avail.
My next recourse, naturally, was the internet. After frantically googling search phrases like "bleach blood bathtub stains" and learning some interesting but ultimately unhelpful factoids regarding the reaction of urine and bleach, I struck gold at this somewhat obscure link. A miracle. You don't even have to scrub. So I thought I'd take some pictures and turn it into an Instructable, surfacing the link more readily for other desperate fools like me.