You can delete the thumbnails folder in the Firefox Profile Folder to remove stored thumbnails.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

You can create a new Boolean pref browser.pagethumbnails.capturing_disabled on the about:config page and set the value to true if you want to disable the thumbnails on the about:newtab page.

• http://kb.mozillazine.org/about:config

You can find your questions using the My Contributions link: https://support.mozilla.org/questions?filter=my-contributions

Thanks for the answer, this is all very technical, so I am wary of making changes.

I had used the online facility (box at top right of New Tab page) to turn-off the thumbnails on the New Tab. I then used auto-config to set New Tab to 'aboutblank'.

On auto-config it now has the following entry :

Name : 'browser.pagethumbnails.storage_version'

Status : 'userset'

Type : 'integer'

Value : '2'

I do not know what the value '2' means and don't know if adding a new item as suggested will cause a conflict with this item.

This is the suggested new item :

Name : 'browser.pagethumbnails.capturing_disabled'

Status : 'userset' ?,

Type : 'boolean',

Value : 'true'

I will add the new entry as above if it is correct, but will it cause a conflict?

Thanks for the 'New Contributions' Link, I have Bookmarked it !

Further to the above, how do I add a new entry to the 'about:config' table ?

You can create new properties in about:config by right-clicking in the list and choosing New > [entry type] from the context menu.

For true/false properties, choose New > Boolean as your entry type.

Thanks for the advice, I have now added the new entry in 'about:config'.

I shall now log out then start a new session, visit a few Sites then log out again.

After that I will come back and report my findings.

Thanks for the advice, I have done a tour round several Sites, using both first page and New Tab, the thumbnails are gone from my PC.

You can also create a Boolean pref with the name browser.pageThumbs.enabled and set the value to false

• resource:///modules/PageThumbs.jsm

Thanks for that tip. If FF updates and reverses the changes, I'll redo what I have done already and add that one too !