How to remove adware from browser?

hi.. my friend just borrowed my notebook. I dont know whats he doing,and now I ended up with annoying browser. ads appear everywhere.my browser slow down. whatever link I click, it will open some ads at first, and I often hear a video without know where does it came from

I try to use avast antivirus full scan.nothing I found.
I try google, use solution from adw cleaner and trend micro. it found the adware and delete it. but those ads still appear.mainly from cityweb

please help me I dont know what to do

Thanks carlos

after trying your suggestion, it improves a lot. not all sites get that adware
but ocasonally,it still appear. not always as before. now just ocasionally.

here I bring the screenshoot when it appear



it appear just occasionaly.so it still annoying.especially when it play video itself

then I do googling to found cyrii uninstall. I found the solution, it just using add or remove program . but this does scare me, as I didnt found cyri on add or remove program. I also didnt find it on your uninstaller,or revo uninstaller I currently used

there are option to download their uninstaler.but i affraid this would made things worse..

what should I do ? thanks

well this happens when you are browsing sites which need you to download something or sign up it installs a spyware don't worry its not a big deal but those things are the ones that brings ads in the first place i know that sometimes they become annoying but you have to make sure what you are downloading since some of them just gather information about you and sells this information for companies

thanks. I will try spybot then install adblock from sven's thread.. let see whats happen

about malware bytes,yes I use it yesterday..but it seems not found the adware

Thanks for all your support.

Last time I try using again,malware bytes, and spybot .on safe mode. They found something. and after I remove, my browser didnt work well ( always crash for few minutes, and often freezing) .so I decided to reinstall both chrome and mozilla frefox.

now I didnt see those kind of ads anymore

thanks a lot

you just have to watch from those websites that requires you to fill a survey or download another file with the main download file