Currently I have 1860px wide image as featured image which shows on top of a post page, and 800px as post content width, and when I
Set $content_width = 800
The featured image shows as 800px wide only
Set $content_width = 1860
Featured image shows well, but embedded youtube video shows as 1860 x 1077, I tried to set
max-width:100% on iframe, it fixed the width, but height still 1077, a
height:auto has no effect.