What is Data Execution Prevention?

I can't access any of my games on facebook, and I can not get onto the yoville.com wedsite I keep getting this pop up thats says windows is shutting down this page, when I clcik for more info it says

Data Execution Prevention
Data Execution Prevention (DEP) helps prevent damage from viruses and other security threats that attack by running (executing) malicious code from memory locations that only Windows and other programs should use. This type of threat causes damage by taking over one or more memory locations in use by a program. Then it spreads and harms other programs, files, and even your e-mail contacts.
Unlike a firewall or antivirus program, DEP does not help prevent harmful programs from being installed on your computer. Instead, it monitors your programs to determine if they use system memory safely. To do this, DEP software works alone or with compatible microprocessors to mark some memory locations as "non-executable". If a program tries to run code—malicious or not—from a protected location, DEP closes the program and notifies you.
DEP can take advantage of software and hardware support. To use DEP, your computer must be running Microsoft Windows XP Service Pack 2 (SP2) or later, or Windows Server 2003 Service Pack 1 or later. DEP software alone helps protect against certain types of malicious code attacks but to take full advantage of the protection that DEP can offer, your processor must support "execution protection". This is a hardware-based technology designed to mark memory locations as non-executable. If your processor does not support hardware-based DEP, it's a good idea to upgrade to a processor that offers execution protection features.
Is it safe to run a program again if DEP has closed it?
Yes, but only if you leave DEP turned on for that program. Windows can continue to detect attempts to execute code from protected memory locations and help prevent attacks. In cases where a program does not run correctly with DEP turned on, you can reduce security risks by getting a DEP-compatible version of the program from the software publisher. For more information about what to do after DEP closes a program, click Related Topics.

How can I tell if DEP is available on my computer?

1. To open System Properties, click Start, click Control Panel, and then double-click System.
2. Click the Advanced tab and, under Performance, click Settings.
3. Click the Data Execution Prevention tab.

Note

• By default, DEP is only turned on for essential Windows operating system programs and services. To help protect more programs with DEP, select Turn on DEP for all programs and services except those I select.

This morning I had no problems, and this has never happened before till now. These sites have never caused me any problems, why is it shutting the down?

 

It's still doing it today.
I've had that happen to me before. But this one is notone of those I believe. But maybe I need to scan for malware prehaps.