i have 2 windows 7 computers, both have three browsers ie chrome opera.
everytime i go to a website searched or input to address bar the website appears but if i click on link inside website a second window appears with an advertisement (various websites various subjects). i have tried the following scans in full and safe mode.
antivirus malwarebytes hitmanpro i have also cleared all cache and reset all browsers.
If they both started behaving the same way at the same time then perhaps your router has been compromised. One way to test for this is to ask a friend or neighbour to pop round with their laptop and see if they get the same problem when connected to your network.
If the default router-access password is something like "admin" or "password" then you need to change that too to prevent the same thing happening again. Just as importantly, when you next access the router with the new password, don't tick the box to remember the log-on details.