angiesdom, thank you very much for pointing out that the extensions worked Ok on Opera 12. I had the User Agent Changer installed for Google to have the latest layout (Google fetches the old layout for Opera 12) - and hence could not install any extension as the download page assumed I was browsing it through Firefox.
I put these two lines into my already functioning AdBlock Plus and the Youtube search bar vanished:
`www.youtube.com##DIV[id="yt-masthead-container"][class="yt-grid-box yt-base-gutter"] www.youtube.com##DIV[id="masthead-positioner-height-offset"]`I had to put the second filter as the first though removed the search bar itself left the empty space behind it in place and since it was space that I was initially seeking when trying to remove the search bar, I needed the second filter to do that job as well. Thanks very much for help as I wouldn't know how to write filter code for the AdBlock myself. Consider the topic solved.