I found pictures on pictures.com. I would like to place them on the web site I am building. Is this legal?

It depends. If the website you found your pictures from aren't copyrighted or plagiarized than it's fine. If not than it's illegal

The web site mentioned is merely a search engine, there are no "photos" on it, it searches using other search engines for photos of any subject you are asking for.
Some come from sites like photo bucket or YouTube where you can share, others were from personal or business web sites where they may be copyrighted, So you will have to check the site where the photos are coming from.

You can't use just any photo from the internet - but there are lots of sites out there where you can find photos that you can use. There are even sites that have photos that you can alter or add to. I have a page about using pictures from the internet. Find out how to know which photos you can and can't use.

http://www.squidoo.com/free-photos-to-use