Effect of using multiple Domain Names

If I have a main site I’ll call mainsite.com and I want users to be able to create a page and back link to it using a name such as mymainsite.com/mypage, or ourmainsite.com/mypage. (I own the domain names mymainsite and ourmainsite)

These secondary domains will be redirected in an htaccess file to the main site so when the user lands, they will land with mainsite.com/ but I will know what page they are controlling.

What is the effect on SEO by doing this? Will the backlinks be counted separately? In that case, am I better off just using mysite.com/mypage?

Thanks

Sorry, I don’t get it. What is the purpose of these other domains again? Why do you want to use subfolders on a different domain, instead of subfolders on the same domain, or query strings on the same domain (like all other referral links used by affiliate programs)?

Just to make it more friendly or more personalized for the user. Not sure yet if I want to go that route, but my question had to do with the SEO aspect of it. If it doesn’t work there, there is no way I would do it.

When a search engine is searching links on another page that refer to your site, the question is do they follow that link through the htaccess file to determine the site the link belongs to.

If it does follow it through the htaccess file, then I do have the option to do it if I decide I want to. I appreciate your concern as to why I would want to do it and I recognize the issues with that. But part of this is to try to understand the SEO process as well.

Thanks

If it’s an actual redirect, I don’t think it would hurt much. If it were an alias, you would probably be dinged for duplicate content.

Yes, search spiders follow Location headers.

Thanks for the input, I appreciate it and it helps.