Fix broken URI fragments and redirects.

docs/4.0/layout/grid.md

@@ -8,7 +8,7 @@ toc: true
 
 ## How it works
 
-Bootstrap's grid system uses a series of containers, rows, and columns to layout and align content. It's built with [flexbox](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Using_CSS_flexible_boxes) and is fully responsive. Below is an example and an in-depth look at how the grid comes together.
+Bootstrap's grid system uses a series of containers, rows, and columns to layout and align content. It's built with [flexbox](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Basic_Concepts_of_Flexbox) and is fully responsive. Below is an example and an in-depth look at how the grid comes together.
 
 **New to or unfamiliar with flexbox?** [Read this CSS Tricks flexbox guide](https://css-tricks.com/snippets/css/a-guide-to-flexbox/#flexbox-background) for background, terminology, guidelines, and code snippets.
 
@@ -46,7 +46,7 @@ Breaking it down, here's how it works:
 - Grid breakpoints are based on minimum width media queries, meaning **they apply to that one breakpoint and all those above it** (e.g., `.col-sm-4` applies to small, medium, large, and extra large devices, but not the first `xs` breakpoint).
 - You can use predefined grid classes (like `.col-4`) or [Sass mixins](#sass-mixins) for more semantic markup.
 
-Be aware of the limitations and [bugs around flexbox](https://github.com/philipwalton/flexbugs), like the [inability to use some HTML elements as flex containers](https://github.com/philipwalton/flexbugs#9-some-html-elements-cant-be-flex-containers).
+Be aware of the limitations and [bugs around flexbox](https://github.com/philipwalton/flexbugs), like the [inability to use some HTML elements as flex containers](https://github.com/philipwalton/flexbugs#flexbug-9).
 
 ## Grid options
 
@@ -151,7 +151,7 @@ For example, here are two grid layouts that apply to every device and viewport,
 {% include example.html content=example %}
 </div>
 
-Equal-width columns can be broken into multiple lines, but there was a [Safari flexbox bug](https://github.com/philipwalton/flexbugs#11-min-and-max-size-declarations-are-ignored-when-wrapping-flex-items) that prevented this from working without an explicit `flex-basis` or `border`. There are workarounds for older browser versions, but they shouldn't be necessary if you're up-to-date.
+Equal-width columns can be broken into multiple lines, but there was a [Safari flexbox bug](https://github.com/philipwalton/flexbugs#flexbug-11) that prevented this from working without an explicit `flex-basis` or `border`. There are workarounds for older browser versions, but they shouldn't be necessary if you're up-to-date.
 
 <div class="bd-example-row">
 {% capture example %}

docs/4.0/layout/media-object.md

@@ -28,7 +28,7 @@ Below is an example of a single media object. Only two classes are required—th
 
 Internet Explorer 10-11 do not render inline elements like links or images (or `::before` and `::after` pseudo-elements) as flex items. The only workaround is to set a non-inline `display` value (e.g., `block`, `inline-block`, or `flex`). We suggest using `.d-flex`, one of our [display utilities]({{ site.baseurl }}/docs/{{ site.docs_version }}/utilities/display/), as an easy fix.
 
-**Source:** [Flexbugs on GitHub](https://github.com/philipwalton/flexbugs#12-inline-elements-are-not-treated-as-flex-items)
+**Source:** [Flexbugs on GitHub](https://github.com/philipwalton/flexbugs#flexbug-12)
 {% endcapture %}
 {% include callout.html content=callout type="warning" %}