Adverts are a reality on the internet. Please screenshot them so we can see if they appear to be normal - it could just be how these sites make extra money.
Hold the power button & tap the home button to create a screenshot - find it in the photos app & post samples here please (via the camera icon on this form).
It is also possible for an internet service provider, or a web proxy, a hacked wifi router etc to inject adverts into browsing 'downstream' so you can try using another internet connection to see if it is the same. Make sure you refresh the page several times to be sure any cached pages are gone.
Also post the full web address to where you see the adverts.