Is this with many websites, some, a few?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Can you post a link to a publicly accessible page (i.e. no authentication or signing on required)?

FredMcD said

Is this with many websites, some, a few? Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Only a few. I have tried the safe mode it doesn't work

cor-el said

Can you post a link to a publicly accessible page (i.e. no authentication or signing on required)?

Here, i uploaded the HTML file https://ferdinandfoundries.com/firefox-help.html

Looks like a formatting issue.

FredMcD said

Looks like a formatting issue.

Can you elaborate? I accessed it from other browser and it looks normal

Look at the picture. Those lines should be on top of one another. But that first line, the header, is not.

Check with the website.

There is no formatting issue with the html, ive been checked it. If there is any formatting issue that cause this. This would happen to my another browser too. This must be firefox problem

Yeah, this is strange. Looks like an issue in Firefox.