For example that .. I have Wordpress installation on http://www.mysite.com and also on http://www.mysite.com/something-related, separated. How Google looks at them, like 2 separated sites or not? When someone links to one of these 2 pages, can the other one get some link juice to? Thank you
I believe Google views them as two separate websites. It's essentially the same as free hosting companies like geocities who use their domain name as part of each user's url. Of course all the pages would show up if you searched for site:www.mysite.com If the pages are linked together, they can help each other a bit.
Google doesn't view them as two separate sites, thats completely wrong. If you don't believe me and want to test it, do something real bad with the first one and see if the 2nd one gets de-indexed also lol.
lol! now I'm more confused ... But people say that if you own a www.mysite.com ( that's just example, just to make sure ) and want to make a forum then if you make it as forum.mysite.com - 2 separated sites, no link juice if you make it as mysite.com/forum then it's still the same site, a lot of webmasters recommend this method because that way you get more free content for your site Should the same rule apply for WP installations ?
A subdomain is more likely to be seen as a new site. Unless you have a massive brand I would go with a folder rather than a subdomain, keeping all the benefit of links pointing to your site under one site. If you have a really strong domain then you could use subdomains to get more listings in google and force out your competitors from the 1st page: http://www.google.co.uk/search?q=seo+book&btnG=Google+Search&meta= For 99% of people this isn't a realistic or viable option though. For your WP installation question, a seperate WP install isn't going to cut it as being seen as a new site if you just install it in a new folder.