This custom HOSTS file by MVPS is used to block web ads by adding a list of hosts serving offensive or malicious content. ad.yieldmanager.com is on that list so the first step is to block it. Then we are going to run a scan with MBAM to check for malicious files on your system. After that I will then instruct you to clean your cookies, clear the browser cache and install SpywareBlaster
which restricts the actions of potentially dangerous sites in Internet Explorer by adding a list of sites and domains associated with known spyware, advertisers and marketers to Internet Explorer's Restricted Sites Zone for additional protection.
That is usually successful but depending on what (if anything) MBAM finds, we may need to take additional steps. But its your choice whether or not to follow the instructions I provide.