how to make a 301 redirect with rewrite if page dont exist

Hello, I want to know how to make 301 redirect with mod rewrite when a requested page don't exist.

for example if the requested page is:
http://www.site.com/sarasa/kakaka.html and this page don't exists I want to 301 redirect to

http://www.site.com/sarasa/sarasa.html

Kind regards,

 

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*) /sarasa/sarasa.html

Code (markup):

If the directory or file does not exist then it uses /sarasa/sarasa.html

However be careful as the content of /sarasa/sarasa.html will show for every unknown URL and return that the page is present (200 status code). At a guess I'd imagine this will cause havoc with search engines.

A custom 404 page may be a better idea:

ErrorDocument 404 /sarasa/sarasa.html

That would show the page you want but return a 404 status code so search engines etc know the page isn't present but visitors still see a nice page to select where to go next.

 

dear @tolra thanks.. a lot.

Let me explain what I'm trying to do. I have many sites that link to my site, this sites sometimes link to incorrect pages, for example: www.sites.com/sarasa/onepage.html and maybe onepage.html doesn't exist so I want to redirect in a 301 way to www.site.com/sarasa/sarasa.html. I that way I don't loose pr...
For other case I'll use the custom 404 page...

this script cover that? if not could you please, help again?

thanks a lot,

 

Actually I made a typo, my apologies, it should have been:

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*) /sarasa/sarasa.html [L,R=301]

Code (markup):

That should 301 any missing page to a single given page, in this case /sarasa/sarasa.html, you should never get a 404.

No idea how search engines will view this, but should be interesting to find out