Smudger. Try deleting your browsing data - history, cache etc. Click the 3 dots top right of chrome, select Settings, then Privacy and Security, then Clear Browsing Data and finally under the heading Basic, tick 'cached images and files' - just the one for a start. If that doesn't work try clearing 'browsing history' next - could also tick 'cookies and other site data' but if you do that you may have to enter your passwords for some sites. John.
PS Did this only happen after you installed Norton?