Natural stone (travertine, marble, etc.) should be cleaned with neutral cleaners. Never clean with any product containing acid, lemon or bleach. Acids, even a light solution of vinegar and water, will eventually etch and damage natural stone
At lease once a year you need to seal the tile and grout. Some products are multi-purpose, meaning you can use the same product on the stone and the grout. Others are just for either the stone or the grout; be sure to read the instructions well, to make sure you are using the proper product.
TIP: Don't use generic cleaning products such as bleach, glass cleaner or degreasers. Don't use vinegar, ammonia, lemon or orange as cleaners. These products that you buy at your local store contain acids, alkalis, and other chemicals that can etch marble and degrade the sealer, leaving the stone more vulnerable to staining. Trying to save money by using these over-the-counter products only ensured that you'll send a lot more time and money in the long run!