When we are navigating the from any SRM business object like SC, RFx,etc to catalog system shows a message pop-up stating "The standards mode is not supported for document modes
less than 8".
The following points could be the reason
Web pages can be displayed in different browser modes by the Microsoft Internet Explorer: They can either use the latest features ("Edge") or in modes compatible with older versions. This can be determined using the "Compatibility View" settings of the Internet Explorer and by the page itself by specifying the mode with the HTML tag "X-UA-Compatible" or by adding it as a header to the HTTP response of the page. Further there is a default logic which changes for the different version of Internet Explorer.
The so determined browser mode is enforced to all embedded IFrames within that page.
Since Unified Rendering requires a "Quirks" for Internet Explorer versions (and thus modes) up to 8 and supports only "Standards" starting from 9 the effective Internet Explorer browser mode needs to be decided before the first page of a Unified Rendering-based application is rendered.
As a solution the URL parameter "sap-ie" is provided by SAP for the supporting technologies. Please find further information about the support in the documentation of the specific application frameworks (such as Web Dynpro ABAP). This is only relevant for Microsoft Internet Explorer.
Add Below parameter under Call Structure for that catalog, before HOOK_URL Parameter:
sap-ie=EmulateIE8 - Fixed Value