Hi guys
I must insert in a html site a htaccess file that create a redirect 301 to
the site home page for every page that gives error 404 (Page not found), but
without affecting the single redirect 301 already present in the file
htaccess regarding other subpage moved and renamed in the past.

The purpose of all of this is not losing the google page rank that can be
passed trough every bad written back link .

What do I write in the htaccess file to do this? Do I have to write it
before or after the existing rules?

Usually I have only one or two error 404 for months to redirect: I wouldn't have to have a penalty for duplicate pages, isn't it?

Thank you

Can we see your current htaccess file? And where do your 404s currently go? (ie, do they present a custom 404 page or do they just give the default 404 error?)

I'll try to help as best I can, but I need a little more info first. thanks.

The initial idea was to not disperse the pagerank google ..
meanwhile thanks the same
bye

Still didn't answer my question.
I was going to help you with a solution if I had more info.