Thanks for the reply.
It helped!
:)

Regards

Previously my SEF was like
www.xxx.com/faq/how-do-i-join-2.htm
www.xxx.com/faq/what-is-this-about-3.htm

Then I went to purge SEF urls,
and all became www.xxx.com/faq/how-do-i-join.htm
xxx.com/faq/what-is-this-about.htm
All without the number behinds.
I have then clear my cache.
And I check the site, all link has point to the NEW links.
But weird enough, after a week.
I still see tons of links with www.xxx.com/faq/how-do-i-join-2.htm (all links with numbers) in 404 logs.
Why is that?

Regards