While Adblock Plus (recommended above) will get rid of the ads which are meant to appear within web pages, it won't get rid of ads which are being loaded by malware (which I suspect is the source of your problem).
Download, install and run the free version of Malwarebyte's Anti-Malware:
http://www.malwarebytes.org/products/malwarebytes_free/
(NB: During the installation process, you'll be offered a trial version of the 'PRO' version. Make sure that you de-select the pre-checked option to take up the offer).
Chris