Simple searches in AltaVista are straightforward: type in a single keyword and the search engine returns a list of links which contain that word.

If what you're looking for is a phrase, just enclose it in quotes. Thus, "mad cow" gets 

     Word count: mad cow: about 5000

     Documents 1-10 of about 3000 matching the query, best matches first.
but the search without quotes gets 
     Word count: cow:155961; mad:246364

     Documents 1-10 of about 100000 matching the query, best matches first.

AltaVista's Help button provides many other tips, and the Advanced button allows much more complex searches and has its own Help button.

Other indexes (ExCite, OpenText, InfoSeek, etc. --check here for access) may turn out to be equally useful. Each has its own proprietary search engine and indexes a different subset of web sites.