Fix anchors, fix naming consistency

I found non working anchors and some naming in consistency. I hope I fixed well. Have a nice day.

docs/layout/grid.md

@@ -48,7 +48,7 @@ If you're using Bootstrap's compiled CSS, this the example you'll want to start
 </div>
 {% endexample %}
 
-The above example creates three equal-width columns on small, medium, large, and extra large devices using our [predefined grid classes](). Those columns are centered in the page with the parent `.container`.
+The above example creates three equal-width columns on small, medium, large, and extra large devices using our [predefined grid classes](#predefined-classes). Those columns are centered in the page with the parent `.container`.
 
 ## Grid options
 
@@ -129,7 +129,7 @@ See how aspects of the Bootstrap grid system work across multiple devices with a
 
 ## Sass mixins
 
-When using Bootstrap's source Sass files, you have the option of using Sass variables and mixins to create custom, semantic, and responsive page layouts. Our [prebuilt grid classes](#example-stacked-to-horizontal) use these same variables and mixins to provide a whole suite of ready-to-use classes for fast responsive layouts.
+When using Bootstrap's source Sass files, you have the option of using Sass variables and mixins to create custom, semantic, and responsive page layouts. Our [predefined grid classes](#predefined-classes) use these same variables and mixins to provide a whole suite of ready-to-use classes for fast responsive layouts.
 
 ### Variables