.htaccess - How To Redirect Non Existing URL's to the HomePage, When my site is in a Sub-directory....? -

i had .htaccess code worked fine when site , files in home root folder, changed new host had domains on it, site in subdirectory , following code no longer works:

rewritecond %{http_host} ^mydomain.com$ [or] rewritecond %{the_request} ^[a-z]{3,9}\ /index\.html rewriterule ^(index\.html)?$ http://www.mydomain.com/ [l,r=301] 

how modify make work, need include subdirectory name in it? right if typed in non existing url "mydomain.com/blahblah567 ....it shows "page not found" type of thing.

thanks

how redirect non existing url's homepage

this enough:

errordocument 404 http://domain.com/ 

or using mod_rewrite in subdir/.htaccess file:

rewriteengine on  rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^ / [l,r=301]