Before every time I use to open a new tab it comes as top site. Now not anymore and instead is an automatically website calle Only Search. I went to Safari preference I change everything and when I quit Safari all the changes are gone.

Question

Every time I used to open a new tab it comes as top site. Now not anymore , instead it open in a website called Only Search, I went to safari preferences and made all changes but after I quit Safari and open again all changes are gone. I can not change anything and new tab comes by it self with other website.

Answer 1

There is no need to download anything to solve this problem.
You may have installed the "Downlite" or "VSearch" ad-injection malware. Follow the instructions on this Apple Support page to remove it.
Back up all data before making any changes.
Besides the files listed in the support article, you may also need to remove this item in the same way:
~/Library/Internet Plug-Ins/ConduitNPAPIPlugin.plugin
One of the steps in the article is to remove malicious Safari extensions. Do the equivalent in the Chrome and Firefox browsers, if you use either of those. If Safari crashes on launch, skip that step and come back to it after you've done everything else.
If you don't find any of the files or extensions listed, or if removing them doesn't stop the ad injection, then you may have one of the other kinds of adware covered by the support article. Follow the rest of the instructions in the article.
The problem may have started when you downloaded and ran an application called "MPlayerX." That's the name of a legitimate free movie player, but the name is also used fraudulently to distribute VSearch. If there is an item with that name in the Applications folder, delete it, and if you wish, replace it with the genuine article from mplayerx.org.
This malware is often found on illegal websites that traffic in pirated content such as movies. If you, or anyone else who uses the computer, visit such sites and follow prompts to install software, you can expect more of the same, and worse, to follow. Never install any software that you downloaded from a bittorrent, or that was downloaded by someone else from an unknown source.
In the Security & Privacy pane of System Preferences, select the General tab. The radio button marked Anywhere  should not be selected. If it is, click the lock icon to unlock the settings, then select one of the other buttons. After that, don't ignore a warning that you are about to run or install an application from an unknown developer.
Still in System Preferences, open the App Store or Software Update pane and check the box marked
          Install system data files and security updates
if it's not already checked.