Your function is working fine. I've checked it with below code:
Sub Main
Dim urls = {"http://zprajnandgaon.gov.in/img/map.png",
"https://image.shutterstock.com/image-photo/colorful-hot-air-balloons-flying-260nw-1033306540.jpg",
"https://losmac.myqnapcloud.com:8081/download/dragdroplistbox.zip",
"https://losmac.myqnapcloud.com:8081/download/inlinepicturebrowser.zip"}
For Each url As String In urls
Console.WriteLine($"'{url}' => {URLExists(url)}")
Next
End Sub
Public Function URLExists(ByVal url As String) As Boolean
Dim webRequest As System.Net.WebRequest = System.Net.WebRequest.Create(url)
webRequest.Method = "HEAD"
Try
Dim response As System.Net.HttpWebResponse = CType(webRequest.GetResponse, System.Net.HttpWebResponse)
If (response.StatusCode.ToString = "OK") Then
Return True
End If
Return False
Catch
Return False
End Try
End Function
Result:
'http://zprajnandgaon.gov.in/img/map.png' => True
'https://image.shutterstock.com/image-photo/colorful-hot-air-balloons-flying-260nw-1033306540.jpg' => True
'https://losmac.myqnapcloud.com:8081/download/dragdroplistbox.zip' => True
'https://losmac.myqnapcloud.com:8081/download/inlinepicturebrowser.zip' => True