Zooming Safari webpages automatically

I am looking for a way to zoom safari webpages automatically and at the same time preserve the format of the page. What I meant by format here is for example in Youtube video pages; I cannot scroll the timeline of videos properly - mouse clicks cannot select timelines properly. Some radio buttons also go missing.

I have been using AllPagesZoom extension but it didn't work well (format problem) and have also tried CSS style sheet but in video pages (I can't scroll properly).

In Safari preferences - the standard font and fixed-width font only changes font sizes of a webpage but not providing an overall webpage zooming effect.

Any ideas or solutions to this Safari Zooming problem ?

 

Working now !

For some unknown reasons to me - CSS Style Sheet works perfectly even on youtube sites !