For any of you posting your vids to the AO3, I have a work skin a pal made for me which makes your vids responsive to the user's browser window size. (You can see it in action on the vids on my account; as you make your browser window larger or smaller the vid window will follow along.)
1. Go to your dashboard and click on "My Skins"
2. Click on "My Work Skins" and then on "Create Work Skin"
3. In the CSS window paste in:
#workskin p.vidwrap {
display: block;
position: relative;
padding-bottom: 56.25%;
padding-top: 30px;
height: 0;
overflow: hidden;
}
#workskin iframe {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
4. Save the skin (name it whatever you want)
Once you've done this, anytime you go to post a new vid, just select the skin you made from the Work Skins field on the post new work form, and then when you're pasting in your embed code, put this around it:
[embed code goes here]
Hope some of you find it useful!