I can open a web site after software installation like this:
[Run]
Filename: \"http://example.com\"; Flags: shellexec runasoriginaluser
Is
For opening a non-executable file after the uninstallation finishes I would write this:
[Code]
const
UninstSiteURL = 'http://example.com/uninstalled.html';
procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
var
ErrorCode: Integer;
begin
if CurUninstallStep = usDone then
ShellExec('', UninstSiteURL, '', '', SW_SHOW, ewNoWait, ErrorCode);
end;