My test website and browsers

As the title reads, I just made a test website where I wrote basic test html code to replace the original InfinityFree html file to see if the page will change. It did.
But in Mozilla (where I did my work with this hosting and file transfer) it shows 403 Forbidden error.
So I thought to wait a 30 mins and check again but still same error.

Then I tried to check on Google Chrome and it worked.

Question: Why is it like that? At first the page worked on Mozilla and later it didn`t.

in my FF works !

but you have errors in code <body> and then <head>

html structure must be