As it says at the bottom of the refpage: "This page is extracted from the OpenCL C Specification. Fixes and changes should be made to the Specification, not directly.". To be specific you will need to propose an MR against OpenCL_C.txt in the OpenCL-Docs repository. CSS changes likewise would need to be done there.
N.b. @bashbaug I think the real problem here is that subgroupFunctions.html is left over from a previous build of the pages and should be removed from the repo - subGroupFunctions.html is the current version.
As it says at the bottom of the refpage: "This page is extracted from the OpenCL C Specification. Fixes and changes should be made to the Specification, not directly.". To be specific you will need to propose an MR against OpenCL_C.txt in the OpenCL-Docs repository. CSS changes likewise would need to be done there.