How to horizontally center a floating element of a variable width?

问题

Edit: I already have this working using a containing div for the floating element and specifying a width for the container (then use margin: 0 auto; for the container). I just wanted to know whether it can be done without using a containing element or at least without having to specify a width for the containing element.

回答1:

Assuming the element which is floated and will be centered is a div with an id="content" ...

<body>
<div id="wrap">
   <div id="content">
   This will be centered
   </div>
</div>
</body>

And apply the following CSS:

#wrap {
    float: left;
    position: relative;
    left: 50%;
}

#content {
    float: left;
    position: relative;
    left: -50%;
}

Here is a good reference regarding that.

回答2:

.center {
  display: table;
  margin: auto;
}

回答3:

This works better when the id = container (which is the outer div) and id = contained (which is the inner div). The problem with the highly recommended solution is that it results in some cases into an horizontal scrolling bar when the browser is trying to cater for the left: -50% attribute. There is a good reference for this solution

        #container {
            text-align: center;
        }
        #contained {
            text-align: left;
            display: inline-block;
        }

回答4:

Say you have a DIV you want centred horizontally:

 <div id="foo">Lorem ipsum</div>

In the CSS you'd style it with this:

#foo
{
  margin:0 auto; 
  width:30%;
}

Which states that you have a top and bottom margin of zero pixels, and on either left or right, automatically work out how much is needed to be even.

Doesn't really matter what you put in for the width, as long as it's there and isn't 100%. Otherwise you wouldn't be setting the centre on anything.

But if you float it, left or right, then the bets are off since that pulls it out of the normal flow of elements on the page and the auto margin setting won't work.

回答5:

You can use fit-content value for width.

#wrap {
  width: -moz-fit-content;
  width: -webkit-fit-content;
  width: fit-content;
  margin: auto;   
}

Note: It works only in latest browsers.

回答6:

The popular answer here does work sometimes, but other times it creates horizontal scroll bars that are tough to deal with - especially when dealing with wide horizontal navigations and large pull down menus. Here is an even lighter-weight version that helps avoid those edge cases:

#wrap {
    float: right;
    position: relative;
    left: -50%;
}
#content {
    left: 50%;
    position: relative;
}

Proof that it is working!

To more specifically answer your question, it is probably not possible to do without setting up some containing element, however it is very possible to do without specifying a width value. Hope that saves someone out there some headaches!