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The best way to post an image is to make it a thumbnail (make sure to check the 'thumbnail' box when uploading your image). That way, a user who clicks on the thumbnail can see a larger version of the photoimage. You can resize the thumbnail in your comment if desired.
Video Posting
We (and MIT) request that video posts are not attached directly to this website. To post a video, please post online on another site, such as YouTube. Once your video is posted on another site, you can include the link into your post, and a still (attached as a thumbnail) from your video if desired.