please help since our website has many mozilla users,hence they want to see the scroll part area with scrollbar thumb by default.For safari and chrome we fixed it using webkit,but not working the same in mozilla

Is this only happening on a specific website or is this a common issue?

On Mac the scroll bars can be hidden and only have them show when you scroll the page so you can see the current scroll position. You can make the scroll bars always visible: System Preferences > General > Show Scroll Bar > Choose "Always"

With OS X 10.13 there can be issues with the scroll bar thumb on some pages, so make sure to update that OS version.

• Bug 1408701 - Firefox scrollbar has no thumb on some pages (on macOS 10.13?)

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)