Domain forwarding and masking. SEO

Dear all:

At the moment I have two domain names: and and I want people going to one of these domains to see the similar content.Both domain names are registered with the same registrar and are on the same hosting plan that I have.

Here is a reply from my hosting company:
domain forwarding.
Domain forwarding lets you automatically direct your domain’s visitors to a different website.
Masking prevents visitors from seeing your domain forwarding by keeping your domain name in the Web browser’s address bar.

I would like to have that masking thing, but I just want to make sure that the “big 3(G,MSN, and Y!)” won’t have any problem with it. Would domain masking hurt my SEO in any way?

Check this out.

Thanks for posting that link, domain masking etc. was something I had been wondering about lately as well, and that article explained things quite well.