There isn't much grosser than the shower curtain that has been hanging in your shower for too long. Most people think of shower curtains as disposable, but they don't have to be. Cleaning a shower curtain is a simple procedure. Just put it in the washing machine on warm with some laundry soap and a little bit of bleach. (Do not put it in the dryer, it will melt.) If you want to dry it with a towel, you can, but it is not neccesary. You will be amazed at the results. An almost brand new shower curtain. It will be a little wrinkled when you pull it out of the washing machine, but they will go away shortly after you hang it.
You can help prevent shower curtain mildew by spraying a mixture of vinegar and water on the shower curtain once you have hung it back up. It is best to spray on the inside. Especially on the bottom and on the bottom of the outside also, as it seems to grow their too. If your children take baths, make sure to pull the shower curtain out of the tub to help prevent more mold and mildew. If you think about the ring you get in your tub from baths, you don't want that same ring on your shower curtain.