If you in meta, there's no clear button to take you back to the main website, same thing when you in the website and you want to go to meta. Meta theme is also so similar to the main website that I sometimes get confused between them.
There used to be a link to Meta in the navigation bar, but it was removed recently. Now, you'll have to expand the StackExchange dropdown to move between Meta and main:
It's not immediately obvious where the links are, but once you find them I think. it's pretty easy to switch between the sites. Note that the link to site you are currently on (in my case Meta) is bolded.
- Feedback request: New top bar and MultiCollider redesign (on MSO)
- A New Top Bar for Stack Exchange (on blog.SO)