css is not loaded on first visit_html/css_WEB-ITnose

jquery mobile:

First visit, no css style loaded. Refreshing can solve the problem, so I added an attribute target="_parent" and the problem was solved.
I want to know why this is. Is there any other method without adding a target?

Reply to discussion (solution)

Not very clear

CSS is in the parent window, the window you see is a child window

CSS is in the parent window, the window you see is a child window
The page pointed to has its own css

Not sure

I understand

Check carefully what target="_parent" means before using it. Don't think that it is added to the page just for functionality.
18 Materials is a very good site. Welcome to use it.

Is it using a frame or something? reason? I feel like it’s not very clear