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I create a simple html that plays a mp4 video. <video controls=""> <source src="https://www.sustainablewestonma.org/wp-content/themes/twentytwelve-child/uploads/video_5dc84eed70712951301402.fixgasleaks" type="video/mp4">Your browser does not support the video tag. </video>On a desktop it works fine. On a Iphone, I get a grey circle with a white triangle in it (the play button). When I push the button the video plays. How do you display the first frame as the default image for the video?

iphone 11 plugged into macbook pro. Bring up safari on macbook to inspect website being displayed on the iphone. two issues: 1) unable to reload css files. Clear cache on both machines, refresh but the old version of the css file continues being used. Is there a hidden cache. THE ONLY WAY SEEMS TO BE RENAMING THE CSS FILE ON THE SERVER. Is this the best apple can do? 2) css files are not shown in develop.