Most often this can be resolved by removing the software causing this. Most of the time this software is a Plug-in (also known as an add-on or extension) installed in your browser. Whilst many of these are helpful some can be malicious. If you do a web search for any plug-in you don't recognise you should be able to find out which category it fits into.
We've copied below links on how to remove plug-ins for the 4 major web browsers
Afterwards you may wish to restart your web browser to remove any settings changed by the software.
If this doesn't work we'd recommend speaking to our Enhanced IT Support desk who should be able to help.