This is a HL7 FHIR server, and as you appear to be accessing this page from a web browser you are seeing a HTML version of the requested resource(s). You can also access this URL from a FHIR client as a ReSTful API call. For more details please see the HL7 FHIR specification.
<?xml version="1.0" encoding="UTF-8" standalone="no"?><CodeSystem xmlns="http://hl7.org/fhir">
   <id value="CareConnect-ListWarningCode-1"/>
   <url value="https://fhir.hl7.org.uk/STU3/CodeSystem/CareConnect-ListWarningCode-1"/>
   <version value="1.2.0"/>
   <name value="Care Connect List Warning Code"/>
   <status value="draft"/>
   <date value="2018-11-01T00:00:00+00:00"/>
   <publisher value="HL7 UK"/>
   <description value="A CodeSystem to identify the reason a list may be incomplete."/>
   <copyright value="Copyright © 2016 HL7 UK"/>
   <caseSensitive value="true"/>
   <content value="complete"/>
   <concept>
      <code value="confidential-items"/>
      <display value="Confidential Items"/>
      <definition value="Items excluded due to confidentiality and/or patient preferences."/>
   </concept>
   <concept>
      <code value="data-in-transit"/>
      <display value="Data in Transit"/>
      <definition value="Patient record transfer from previous GP practice not yet complete; any information recorded before dd-mmm-yyyy has been excluded."/>
   </concept>
   <concept>
      <code value="data-awaiting-filing"/>
      <display value="Data Awaiting Filing"/>
      <definition value="Patient data may be incomplete as there is data supplied by a third party awaiting review before becoming available."/>
   </concept>
</CodeSystem>