I can not fill in the blanks in my code

I wrote code. I can't fill in the blanks in my code. Why I can't do it?

...

<style type="text/css">
...

#content
{
    margin: 0px;
    padding: 0px;
    width: 100%;
    background-color: black;
    color: white;
}

...

<div id="content">
AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>AAAAAAAAA<br>
</div>

My site's address is http://www.clover.lrv.jp.


This is due to a browser pre-set margin. Put this at the top of your code, it will reset the margins and padding:

*{margin: 0; padding: 0;}