2.2.58 [HTML5:2014] Section 7.5.3 Processing model

C0075: The fallback assigns an access key which is based on the x-ms-acceleratorKey

The specification states:

 ... Processing model
     ...
     Whenever an element's accesskey attribute is set, changed, or removed, the user agent 
     must update the element's assigned access key by running the following steps:
         ...
         ... Fallback: Optionally, the user agent may assign a key combination of its 
         choosing as the element's assigned access key and then abort these steps.

IE11 Mode and IE10 Mode (All versions)

The fallback assigns an access key combination which is based on the x-ms-acceleratorKey.

C0076: The fallback option to assign a key combination as the access key is not used

The specification states:

 ... Processing model
     ...
     Whenever an element's accesskey attribute is set, changed, or removed, the user agent 
     must update the element's assigned access key by running the following steps:
         ...
         ...  Fallback: Optionally, the user agent may assign a key combination of its 
         choosing as the element's assigned access key and then abort these steps.

IE9 Mode and IE8 Mode (All versions)

The fallback option to assign a key combination as the access key is not used.