"oneclickads" is opening pages in chrome and Firefox as well.
 

HK i have elementary freya os in my lap top and suddenly oneclikads is opening different unwated sites. How to remove it ???

One way of blocking the advertising sites is to edit /etc/hosts. If you add, for example, the line
127.0.0.1 ad.doubleclick.net
then every time a site tries to divert you to something at ad.doubleclick.net, your computer replaces the address with 127.0.0.1 -- that's your own computer, so the page is not found.

thank you for replay . i am new to linux so not sure what to do now...
this is how looks my hosts.

127.0.0.1 localhost
127.0.1.1 tovp-tuk

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Personally (for FF), I use the add-ons 'NoScript' and 'Adblock Plus'.
They work a treat :)

Download & install 'Ad Block Plus' in your browser.

Add the necessary line at the end of the file. I gave the example
127.0.0.1 ad.doubleclick.net
or I could have used
127.0.0.1 googleadds.g.doubleclick.net
Just isolate the bit between Http:// and .net (or .com or whatever) in the offending link.

I didn't recommend an add-blocker, because I don't know what browser you have. If you're using one that offers add-blocking, that will be best. Look in the browser's menu for "Tools- addons" or "Extensions" or even just go to "Help".

thank u for ur advices. Adblock plus is working nicely.
Hare Krishna

Late, but my preference is for Ghostery. It blocks all trackers, not just ads.

You can get a good hosts file designed to block ads here. The maintainers of the file update it periodically. I've used it for years and it works as well on Linux as on Windows.

Simply add the relevant portion, everything from this line down

to your /etc/hosts.

I did remember that, but couldn't find the address. I've never created such a large hosts file, as I've always presumed it would slow the computer and this one's slow enough already.