OK – I have not delved too deeply into the code yet but I can tell you that this is all to do with enabling the ability to resize rather nicely and fluidly to different device real estate. At least that seems to be the suggestion I am looking at.
I pasted a youtube and vimeo link into the forum post and the videos are wider than the forum . Why dont the videos fit within the forum width ?
they typically do… wp made a mistake when they removed the size option… but more importantly, other plugins, such as jetpack mess up the width… any chance you are running jetpack? if not, can you give us a link to an example so we can examine the html/css?