CSS Problem Simple

I have absolutely no idea why this isn't working. I'm trying to align the navigation and content of a website, navigation is fine at the moment.

Problem: Whatever I change in the CSS for content does not affect the class in the other page.

<div class='content'>
 aslkdhal;kshl;kasdkjasdhkjlashkjashdkjalsdklajsd
</div>

div.content{
  margin-left: auto;
  margin-right: auto;
}

I'm sure it'开发者_StackOverflow社区s simple. Thank you in advance.

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You're right, it is simple. You just need to specify .content's width.

margin-left: auto;
margin-right: auto;

centers the div itself, not the content.