Hi.
Why sometimes this site shows one and other times other appearance ? How to fix only one to show ?

 

You have to log in for your preference to stick, I believe.

 

In the bottom screenshot you are not logged in, so you are stuck with the default scheme which is the hideous orange. So if you only want to see one, then you need to change your personal preference (which is used when you are logged in) to the hideous orange scheme. You can do this by going down to the bottom left corner of the page (when logged in) and clicking on the "Style Chooser" (which probably says "vB 3.x Fluid") and selecting "AAC Updated v3".

 

Thanks.
When I log in with the orangy screenshot (which I do not like), shows my 'avatar' at the upper right corner as 'signed in' but does not allow me to navigate in the site nor post.
Will follow your suggestions.