ASP.Net website and SEO

[mantech]

Dear All,

I need some information regarding the ASP.NET Website and SEO.(I dont have any sense regarding the SEO)

In my website, when user visit first time to the website, there is a splash page. And  until and unless you dont enter email address
it does not allow you to enter inside the site.

So my Question is, Is there any problem of this splash page to SEO? If yes, Please give me some solution/options on the same.
Can we do SEO for Authenticated pages?

Thanks...