Strange sidebars on Blog, Posts and Posts categories

Hi, instead of the sidebars shown on your demo for blog, posts and posts categories

I see this strange thing

How can I fix that?
(i’m still doing anything on the imported demo, just studying how it is before doing my own website)
In other words, how can I manage the sidebar for posts categories and blog?
I mean, I read your documentation but I dont understand this strange behaviour.

Ok, i think I fixed. there was a block widget with a strange code. Probably a bug from demo importing.
thanks anyway for any clarification.

Thank you for taking time to confirm back.