Analytics code and Header Code

Hello, first of all i love this theme.

But i need a small tutorial, i don´t know what means the option: archive header.

Another small problem is that i put analytics code in the section Header code. Is that the right place?

It seems Google Analytics detects the code, but sometimes i analyze the page with Seo Quake (chrome extension for SEO) and it doesn´t detects the analytics code…

I have another sites but they don´t have this problem.

Can you help me about this? Must i worry about this problem or maybe the analytics code is ok?

Thanks.

Best regards.

David