You are not entitled to remain in the U.S. beyond the time indicated on the I-94 card, unless you have an extension of stay. If you violate the terms and conditions of your visa, and you wish to apply for permanent residency, you will not be able to adjust your status in the U.S. to that of a permanent resident, but you will have to leave the U.S. and apply from overseas. There is an exception for those awaiting employment authorization. The Immigration and Naturalization Service may allow you to start working if you have not received a response to your application within 60 days. Typically, you can work for three months on a temporary work authorization card.
Most visas also allow for extensions.
Again, the number and length of the extension will depend upon the visa. Simultaneously In order to qualify for a nonimmigrant visa you must not intend to stay in the U.S. permanently. The information found in this web site is for information only, and neither constitutes formal legal advice, nor gives rise to an attorney-client relationship. Immigration Legal Services, disclaims any and all liability resulting from actions due to reliance upon the information contained in this web site.