uses WinInet;
function GetWebPage(const Url: string):string;
var
  Session,
  HttpFile:HINTERNET;
  szSizeBuffer:Pointer;
  dwLengthSizeBuffer:DWord;
  dwReserved:DWord;
  dwFileSize:DWord;
  dwBytesRead:DWord;
  Contents:PChar;
begin
  Session:=InternetOpen('',0,niL,niL,0);
  HttpFile:=InternetOpenUrl(Session,PChar(Url),niL,0,0,0);
  dwLengthSizeBuffer:=1024;
  HttpQueryInfo(HttpFile,5,szSizeBuffer,dwLengthSizeBuffer,dwReserved);
  GetMem(Contents,dwFileSize);
  InternetReadFile(HttpFile,Contents,dwFileSize,dwBytesRead);
  InternetCloseHandle(HttpFile);
  InternetCloseHandle(Session);
  Result:=StrPas(Contents);
  FreeMem(Contents);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
edit1.Text := GetWebPage('http://www.baidu.com/');
end;