It is possible, even on major web sites, to have an automated advertisement push malicious code and pop-up advertisements to innocent web users. If you see a pop-up advertisement that looks suspicious, fight the reflexive urge to close the pop-up window. The "X" icon on that window is most likely not going to close the window, but rather will launch malicous code on your computer. DO NOT click anywhere within the pop-up window itself.
Try to close a malicious web browser session by right-clicking on the icon for your web browser in your Task Bar (the bottom bar of your screen which displays the programs you have running), then select close. If the page does not close, make sure you've saved your work in other windows and then restart your computer.
If you are at all uncertain about how to respond to a pop-up advertisement, please call your professional IT support team (C&G Consulting's Support Center is reachable at 262-522-8226) so we can try to safely restart your computer before it becomes infected.