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.
{
  "resourceType": "ValueSet",
  "id": "CareConnect-AllergyVerificationStatus-1",
  "extension": [
    {
      "url": "http://hl7.org/fhir/StructureDefinition/valueset-map",
      "valueReference": {
        "reference": "https://fhir.hl7.org.uk/STU3/ConceptMap/CareConnect-AllergyVerificationStatus-1"
      }
    },
    {
      "url": "http://hl7.org/fhir/StructureDefinition/valueset-sourceReference",
      "valueUri": "http://hl7.org/fhir/ValueSet/allergy-verification-status"
    },
    {
      "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
      "valueCode": "pc"
    },
    {
      "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
      "valueInteger": 3
    },
    {
      "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-ballot-status",
      "valueString": "Informative"
    }
  ],
  "url": "https://fhir.hl7.org.uk/STU3/ValueSet/CareConnect-AllergyVerificationStatus-1",
  "identifier": [
    {
      "system": "urn:ietf:rfc:3986",
      "value": "urn:oid:2.16.840.1.113883.4.642.3.115"
    }
  ],
  "version": "3.0.1",
  "name": "AllergyIntoleranceVerificationStatus",
  "status": "active",
  "date": "2017-04-19T07:44:47+10:00",
  "publisher": "HL7 (FHIR Project)",
  "contact": [
    {
      "telecom": [
        {
          "system": "url",
          "value": "http://hl7.org/fhir"
        }
      ]
    }
  ],
  "description": "Assertion about certainty associated with a propensity, or potential risk, of a reaction to the identified substance.",
  "copyright": "Copyright © HL7.org 2011+",
  "compose": {
    "include": [
      {
        "system": "http://hl7.org/fhir/allergy-verification-status",
        "concept": [
          {
            "code": "unconfirmed",
            "display": "Unconfirmed"
          },
          {
            "code": "confirmed",
            "display": "Confirmed"
          }
        ]
      }
    ]
  }
}