When doing Google search I noticed that the image preview appears next to the search result.
As this is slowing down the search itself and the image preview is not informative at all, I looked for a way of disabling it.
This was not a feature of Google as the search on another computer didn't show the page preview.
It appeared that the add-on CyberSearch 2.3.0 (that I had installed in my Firefox) adds page previews on search engine result pages. Disable the add-on to restore normal Google search.
There is an option to disable the page preview within the add-on itself.
Go to Add-ons/Extensions/CyberSearch/Preferences/Behavior/
uncheck Show thumbnails on search result page
The CyberSearch is a quite useful add-on, e.g. it enables instant search in your address bar, also it enables to easily restrict search to only one site through address bar.