Excerpt from the license agreement, http://www.wolfram.com/legal/agreements/wolfram-mathematica.html:
Limited Warranty and Disclaimer
WRI warrants that the Product shall be free from defects in the physical media for a period of 90 days following the date of purchase when used under normal conditions. You acknowledge that WRI shall provide, as Your sole remedy for breach of this warranty, another copy of the physical media. The foregoing warranty is in lieu of all other warranties, express or implied.
WRI does not warrant that the Product is free from all errors and/or omissions, and in fact it may contain them. Except as specifically set forth above, the Product is provided "as is". WRI makes no representations or warranties, express, statutory, or implied, with respect to the Product or the Software contained in the Product or data accessed thereby, including, without limitation, any implied warranties of merchantability, interoperability, or fitness for a particular purpose, all of which are expressly disclaimed. WRI does not warrant that the functions contained in the Product will meet Your requirements or that the operation of the Product will be uninterrupted or error free.
WRI, and its agents, representatives, and independent contractors, shall not be obligated to provide or liable, under any circumstances, for providing information on or corrections to errors and/or omissions discovered at any time in the Product, whether or not they were aware of the errors and/or omissions. WRI does not recommend the use of the Product for applications in which errors and/or omissions could threaten life, injury, or significant loss. Some states do not allow the exclusion of implied warranties, so this may not apply to You. This warranty gives You specific legal rights, and You may also have other rights that vary from state to state. This Agreement is governed by the laws of the State of Illinois in the United States of America without effect to any choice of law provisions.
In no event shall WRI or its agents, representatives, and independent contractors be liable for any lost profits, lost use, lost benefits, or any consequential, indirect, incidental, special, or punitive damages, whether in contract, tort, or otherwise, even if WRI has been advised of the possibility of such damages. WRI's cumulative liability to You or any other party for any loss or damages resulting from any claims, demands, actions, or otherwise arising out of or relating to this Agreement shall not exceed the license fee paid for the Product. Some states do not allow certain limitations of damages, so the above limitations may not apply to You.
You should read the agreement that came with your copy of Mathematica, in case it differs. On a Mac, it can be accessed through the menu, Mathematica > About Mathematica... (or About Wolfram Mathematica...). This brings up a palette with a "License Agreement" button that will display the license agreement.