How to Open HTML File 

//--------------------------------------------------------------------------------
// HTMLView - This sample shows how to open HTM/HTML file with default browser.
//            It uses ShellExecute Win32API function with 'open' parameter,which
//            causes system to look through registry for a program, which is
//            attached to HTM/HTML extension.
//-------------------------------------------------------------------------------
unit HTMLUnit;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ShellAPI;
type
  TForm1 = class(TForm)
    OpenDialog1: TOpenDialog;
    Button1: TButton;
    Button2: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1    : TForm1;
  HTMLFile : Array[0..79] of Char;
implementation
{$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
begin
 If OpenDialog1.Execute then
   begin
// get name of selected file
    StrPCopy(HTMLFile, OpenDialog1.FileName);
// allow user to open (i.e. view) it with browser
    Button2.Enabled := True;
   end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
// run ShellExecute function with 'open' paramemter
 ShellExecute(Handle, 'open', HTMLFile, nil, nil, SW_SHOWNORMAL);
end;
end.