div.Section1 
{ 
position: relative;
width: 70%;
margin-right: auto;
margin-left: auto;
} 




<!---------------------------------------------------------------------- 

to wklejamy do pliku HTML 

<link rel="Stylesheet" type="text/css" href="word_center.page.css">

----------------------------------------------------------------------->





<!---------------------------------------------------------------------- 


to wklej do pliku HTML przed </head> -----------------------------------

<style type="text/css">
div.Section1 
{ 
position: relative;
width: 70%;
margin-right: auto;
margin-left: auto;
} 
</style> 

------------------------------------------------------------------------->