Jim,

If it is regular ceramic tile, I would make sure the grout has a sealant and hopefully it was installed with a mildew reducer. A simple spray bottle of white vinegar and water cleans well and makes the tile shine. Here is a link with some "recipes".

http://organizedhome.com/content-8.html

http://www.thenewhomemaker.com/vinegar

I use it on many items in my home including the hardwood floors. It is also an approved "green" product and I am for anything that helps the environment and does a good job. You will have a vinegar smell but it subsides quickly. Simple, inexpensive and works--my kind of product!