You can turn off the popunder ads in your account settings and those ads should go away.

I tried uploading a webm. Site says "Filetype not allowed. The admin is accepting complaints regarding this right now. [...] An error occured. The image could not be added because it already exists or it is corrupted." What's up?

Wrong upload page.

Oh... Thank you.

What do we do when a child trait represents to parents?

For example:

gelbooru.com/index.php?pa...t&tags=arms_held_back is a child of these three

gelbooru.com/index.php?pa...st&tags=arm_held_back
gelbooru.com/index.php?pa...amp;tags=arms_behind_back
gelbooru.com/index.php?pa...s=list&tags=arms_held

Arms_held in turn is a child of gelbooru.com/index.php?pa...;s=list&tags=arm_grab

Do we still put the parents or does the child replace them to avoid clutter?

The only implication is box_tie implicates arms_behind_back. These tags do not have any parent/child relationship here so nothing need be done.

Edit: arms_held does not appear to be a valid tag and may be purged in the future.
Edit 2: arm_holding appears to be the correct tag for The act of holding another character's arm. For a character holding on to their own arm, use holding_arm.

Why are the WebMs almost always bigger than they should be?

What is source spam, why I can't change any tags\ratings? Didn't get any notices from moderators or anything.

Usually source spam means using the source field to advertise a product or service. For example, certain hentai sites have uploaded a large number of posts (usually short clips from JAV's) to Gelbooru and used the source field to point back to their site.

First of all, this is problematic because those are not acceptable sources - in the case of JAV's, like these sites would upload clips from, the source should either be the JAV name or the contextual page on the official publisher's site about the video. Third-party sources are not sources. The source link isn't a "here's where you can download this content from" link, it's used in the same way as sources in an academic paper: to acknowledge the original creator.

Second, this is problematic because if you're going to advertise on Gelbooru, you need to pay us. If we have reason to suspect that someone's using Gelbooru to advertise their own site without explicit permission from the site owner, that's basically grounds for an immediate ban.

If it wasn't you that did this, IP addresses usually aren't permanent. It's likely that someone on the same ISP or VPN as you did it, got banned, and eventually your ISP or VPN rotated the IP addresses and you ended up with it. Unfortunately, since we have no way of actually knowing if this was the case, we usually cannot remove the ban and you will need to wait until your IP rotates again.

I think I linked to the original work on a few images. How is that advertising if the image comes from an anonymous artist who is known to post on a certain anonymous image board?