ErrorDocument 404 http://your_website.com/error404.phpIt appears that the first line returns 302 Found header code and then redirects to your 404 page. - a really bad thing from a SEO standpoint which gets penalized. More info on how to fix it here: 302 hijacking
ErrorDocument 404 error404.php
The second line gives you the normal 404 page returning a proper 404 header code.
It also appears that using too many 301 redirects cause penalty. But how's that?
Can you recognize this code?
RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]You may know that it's OK when you have several empty PR5 domains to redirect them to your website via 301 temporary header redirect. But what happens if they already have some kind of penalty applied. Well it automatically transfers to your new domain, because as you've might noticed 301 is actually a PERMANENT redirect.
One must be really careful about these things. Now go ahead and fix all your 404 and 301 redirect headers!!! by Nevyan Neykov