Sign ups and logins elegantly in both code and user experience

I've been working on the login and signup part of my website. It was going pretty well. First I made the login form on the same page as the websites homepage, and the signup page open up in a new link. I got some javascript to help check it out and display errors before sending to be checked again in php.

But then I started working on what my website might look like, and I wasn't so keen on having the sign in form on the home page.

When you have a sign in form you need, the email input, the password input, the remember me checkbox, and the forgot password link. Which is a lot of stuff to have on your page, and limits how it would look. So I thought I might just have a login button that pops up a login form.

Now I've done that, I'm not sure how to handle it. I thought I'll send it to a separate login controller, and that could check to make sure it's ok, then redirect the user back to the homepage if there were errors. But then I have to know to have the login pop up box open and show the errors. And I'm not sure how to do that. It seems a bit messy too. [edit where I say "know to have the login pop up box open" I already know how to do that with javascript but I mean as it is redirected it needs to know that the user has already opened it.]

So I'm asking for advice, on if I were to do the popup box how would I handle it, with regards to breaking things up into different controllers. Also some general advice on handling logins and signups in an elegant way, but that's still pretty simple for a beginner like me. I'm trying to make a pretty complex website and the way I'm going I'll still be on the login form next year!