Question: When I change tabs (or, as I just found out while clicking this text box to write this question) click on some elements on a web page like a text box, firefox just opens up a new tab with this link in the address bar

```
http://ad.yieldmanager.com/%5BMACRO%5Dhttp://stage.traffiliate.com/TrafficCop.aspx?CampaignUid=1d1fe647a02224c1&SourceId=355&CreativeId=18305031&LineItemId=5706215&PublisherId=544347&SectionId=4829179

```

It's driving me insane  

Is it a virus or some setting I enabled accidentally? I don't have any addons installed and Firefox is 13.0.1  

Any clue on how to find out what exactly is causing this tab to open up, seemingly at random times? The page always says Not found on it 

PS: Why is the link above that I put in as Quote changing automatically to hyperlink? How do I convert it to text?

Answer: 
Could be anything, but I might provide a few suggestions.

1. Try a [portable version](http://portableapps.com/apps/internet/firefox_portable) of your browser to ensure it's not Firefox alone. Maybe even reinstall your browser, if you don't mind the effort.
2. Check your Firefox addons and remove all suspicious sounding extensions you don't need.
3. Try to block those advertisement via addons like [AdblockPlus](https://addons.mozilla.org/en-us/firefox/addon/adblock-plus/).
I read this might help [here](http://forums.majorgeeks.com/showthread.php?t=147662). Althought you might need to add the url to be blocked.
4. Maybe use tools to scan for malware (maybe [AdAware](http://www.lavasoft.com/)) etc.
5. Make sure you don't have one of those addon bars installed by accident. I remember only stuff like ebay or ask.com toolbars.

**I am pretty confident, that option 2/3 might solve your problem.**
In FireFox, type **about:config** in the address bar.
Then search for that web address. Maybe an add-on or hidden setting has set it somewhere.