It is important that you cite your work as you go. By keeping track of author and title information, you can more readily locate information you have used and may need to locate again for future reference.
Do not use a URL as your only citation. You may not be able to locate the site again if you didn't copy the URL correctly. Make sure you include the title of the website and the author in any preliminary citation you create.
An in-text, or parenthetical citation, follows a direct quote or reference to the work of another and gives credit to the originator of that quote or idea.
Parenthetical citations occur in the body of your paper. These citations refer to resources included on your works cited page.
For more information and to check your citations, check out the Purdue OWL's "MLA In-Text Citations: The Basics."
The online reference manual from Diana Hacker also has helpful examples of in-text citations.