i am doing a works cited for my essay and one of my articles was from wikipedia online. what do i do if i can't find an author?
At the bottom of the Wikipedia page is likely a set of Footnotes or a small bibliography, you may want to search amongst those accredited websites to see if you can find the information and then state the author of that site as the source. As a general rule though, teachers don't usually like Wikipedia because it is an openly editable source of information and as such can often be biased or just wrong, that is unless your teacher has explicitly said that it's ok. Other than that, usually if you cannot find an author for a bibliography in MLA format you can substitute the title of the work or article.
Thanks. I have one more question: How do I cite a page in a textbook?
The same you would any book, it's not a multi-volume work or an encyclopedia so just use the standard MLA format. You shouldn't have any problem finding the author in a well-formed text book.