Why doesn't this CSS :first-child selector wor

问题:

I'm working on an Asp.Net MVC 3 project and have run into a brick wall on why this doesn't work like I think it should.

My markup is:

<fieldset>
    <input type="hidden" value="2">
    <div class="editor-label"> 
        <label for="Name"> Name</label>
    </div>
    ...
</fieldset>

My css is:

.display-label, .editor-label
{
    margin: 0.8em 0 0 0;
    font-weight: bold;
    display: inline;
}

fieldset > div:first-child
{
    margin: 0;
}

All I want to do is make the first div in the fieldset have a margin of 0. I thought that the selector fieldset > div:first-child would apply the style to "the first child of a fieldset, whose type is a div", but apparently something is eluding me.

I've tried this in IE9/FF/Chrome so it's not an old browser messing with my selectors.

Thanks.

回答1:

fieldset > div:first-child means "select the first child element of a fieldset if it's a div".

It does not mean "select the first div in the fieldset".

The first child in this case is <input type="hidden" value="2">.

To select that div without changing the HTML, you need to use fieldset > div:first-of-type.

Unfortunately, while :first-child is widely supported, :first-of-type only works in IE9+ and other modern browsers.

So, in this case, the best fix is to continue using fieldset > div:first-child, and simply move <input type="hidden" value="2"> so that's it's not the first child.