What to do:
Use an AdBlocker to prevent being shown ads, and avoid possible malware infection.
Why do it?
Attackers can inject malicious code or malware-filled ads into legit online advertising networks and websites. This is called malvertising and it can infect your computer.
Some websites rely heavily on ads for revenue and ask that you sign up to their website (so they can send you marketing material), or disable the ad-blocker software. You can temporarily disable the ad-blocker for the website so you can continue to access their content. Bear in mind that your PC would be vulnerable to malvertising for the duration of the ad-blocker being disabled.