Put a div centered

HTML & CSS
1 

<div style="background-color:pink;min-height:100px;[COLOR="Red"]text-align:cente[/COLOR]r">
  <div style="background-color:yellow;min-height:50px;width:100px">yellow</div>
  my text<br>
  <input type='text'>
</div>

My text and input box is centered with the code above.
But the yellow div is not centered in display.
How can I make it to be centered.

temperal url http://dot.kr/x-test/01.php

2

set the left and right margins of the yellow div to auto and that will centre the div.