mdn/content

MDN URL https://developer.mozilla.org/en-US/docs/Web/API/Element What specific section or headline is this issue about? No response What information was incorrect, unhelpful, or incomplete? -- What did you expect to see? As the title says Do you have any supporting links, references, or citations? The details are read-only. Do you have anything more you want to share? No response MDN metadata Page report details Folder: en-us/web/api/element MDN URL: https://developer.mozilla.org/en-US/docs/Web/API/Element GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/api/element/index.md Last commit: 868de6e Document last modified: 2026-09-12T19:13:32.000Z

MDN URL https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/CSS_layout/Practical_positioning_examples What specific section or headline is this issue about? #Changes to the existing CSS What information was incorrect, unhelpful, or incomplete? "Next we need to make some small changes to the existing CSS, to get the info-box placed and positioned. Change your .info-box rule to get rid of margin: 0 auto; (we no longer want the info-box centered), add position: fixed;, and stick it to the top of the browser viewport." However, in the example code block right below this description, margin: 0 auto; was not removed: What did you expect to see? An example code block with the margin: 0 auto; rule removed: .info-box { width: 452px; height: 400px; position: fixed; top: 0; } Do you have any supporting links, references, or citations? No response Do you have anything more you want to share? No response MDN metadata Page report details Folder: en-us/learn_web_development/core/cs

MDN URL https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/img What specific section or headline is this issue about? Supported image formats What information was incorrect, unhelpful, or incomplete? For each image format the section claims that it's a good choice except for WebP, which is excellent, and SVG, which has no information on whether the choice is good. Below it recommends some formats over others even though the others are "good choice"s. Furthermore, choices can only be "good" if there are others which are "bad" but there are no "bad choice"s. The summary in Supported image formats may make the reader question things such as: Why is GIF is a good choice for simple images and animations while WebP and AVIF are recommended and perform much better? And what is meant by "simple"? Why are PNG and JPEG good choices while WebP and AVIF perform much better? Aren't they bad choices then? Is WebP and AVIF also recommended over APNG? What does "high performance" in

MDN URL https://developer.mozilla.org/en-US/docs/Web/API/Element/keyup_event What specific section or headline is this issue about? the keyup event has a non documented and unexpected behavior What information was incorrect, unhelpful, or incomplete? With the keydown event, its property, 'e.ctrlKey' will be reported correctly, however with the keyup event, it doesn't set the ctrlKey property at all, regardless of if they keycode is ctrl or not. Is this intended behavior that's simply not documented anywhere? What did you expect to see? I expected to see a disclaimer about this strange behavior. Do you have any supporting links, references, or citations? umm see below Do you have anything more you want to share? super short html snippet that replicates it. This behavior doesn't make any sense and to me is this way on both firefox and chromium, versions 152.0 and 150.0.7871.186 respectively. So I feel like it should be documented. Is this truly the intended ecma standard? <head> <scri

MDN URL https://developer.mozilla.org/en-US/docs/Web/API/Window/screenX What specific section or headline is this issue about? No where is it spelled out this doesn't actually work What information was incorrect, unhelpful, or incomplete? As far as I can tell the spec requires screenX and screenY to be the left and top most position on the screen of the web page's content. But, testing Safari, and Firefox, and Chrome, none of them adjust screenX and screenY to take into account toolbars or sidebars. All 3 browsers have options to turn on bookmark bars and sidebars. Turning them on does not change screenX nor screenY even though the web content moves left/right/up/down based on those settings. I don't see anything in this spec which allows this behavior, though maybe I missed it. What did you expect to see? Something that called out none of the browsers implement the spec Do you have any supporting links, references, or citations? You can use the example in the article itself. the blue