This webpage references the percentage of the purchase price of futures contracts (that can be purchased on margin) that the investor must pay for with his or her own cash or marginable securities. Specifically, these refer to the initial margin requirements.
http://www.openecry.com/traderstoolbox/margins.cfm
To access the information, click on the tab to display the details for each group and use the vertical scroll bar (on the right side of the window) to move up and down the page. Refer to the Figure below.