I'm writing a book and I wanted to know can you use newspaper clippings , and jokes off the web as long as you site your source

You can use excerpts if you cite your source, but you shouldn't use "used by permission" unless you actually have permission.

Jokes off the Web are fair game. For safety gather your clippings and figure out how many papers and/or magazines are involved. Some actually include phrases on the title page on the lines of "extracts and quotes from this publication may used with attribution"
BUT
They are more likely to say "no part of this publication may be extracted or quoted without the express permission of the publisher"