: 
1)   "  "   : images, JS, style. 
2)    .txt      . 
3)           , :               . 
4)                DOCTYPE (  ->  ): 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

5)      1 . ,     "".
.