Facebook uses an HTML element called a DIV to suggest new friends in the People You May Know box. You can't disable this functionality on Facebook's side, but you can prevent your Web browser from displaying the DIV element by using Adblock Plus. You can block the DIV with the help of the Adblock Plus Element Hiding Helper tool. The tool is included in Adblock Plus for Google Chrome, but it must be installed in Firefox. There is no way to hide Web page elements using Adblock Plus for Internet Explorer.
Open Facebook in Google Chrome, click the Adblock Plus icon and select Block Element to use the Adblock Plus Element Hiding Helper tool.
Mouse over the top of the People You May Know box located to the right of the box title and click once when the entire box is selected. The box is highlighted in yellow when it is selected.
Click the Add button to create a new Adblock Plus filter and enable it. The People You May Know box is hidden immediately; you don't need to restart the Web browser.
Open the Element Hiding Helper For Adblock Plus page on the Mozilla Add-Ons website and click the Add to Firefox button. Click the Install Now button to install the extension -- no restart is required.
Click the Adblock Plus button and choose Select an Element to Hide from the drop-down menu to use the Element Hiding Helper tool.
Mouse over the People You May Know box and click it when the entire box is surrounded by a red outline.
Click the Add Element Hiding Rule button to hide the People You May Know box immediately. You don't need to restart the Web browser. The rule is used every time you open Facebook in Firefox.