[html] What is syntax for selector in CSS for next element?

If I have a header tag <h1 class="hc-reform">title</h1>

h1.hc-reform{
    float:left;
    font-size:30px;
    color:#0e73bb;
    font-weight:bold;
    margin:10px 0px;
}

and after that I have a paragraph <p>stuff here</p>.

How can I ensure using CSS that every <p> tag that follows the h1.hc-reform to use: clear:both;

would that be:

h1.hc-reform > p{
     clear:both;
}

for some reason that's not working.

Not exactly. The h1.hc-reform > p means "any p exactly one level underneath h1.hc-reform".

What you want is h1.hc-reform + p. Of course, that might cause some issues in older versions of Internet Explorer; if you want to make the page compatible with older IEs, you'll be stuck with either adding a class manually to the paragraphs or using some JavaScript (in jQuery, for example, you could do something like $('h1.hc-reform').next('p').addClass('first-paragraph')).

More info: http://www.w3.org/TR/CSS2/selector.html or http://css-tricks.com/child-and-sibling-selectors/

You can use the sibling selector ~:

h1.hc-reform ~ p{
     clear:both;
}

This selects all the p elements that come after .hc-reform, not just the first one.

no > is a child selector.

the one you want is +

so try h1.hc-reform + p

browser support isn't great

The > is a child selector. So if your HTML looks like this:

<h1 class="hc-reform">
    title
    <p>stuff here</p>
</h1>

... then that's your ticket.

But if your HTML looks like this:

<h1 class="hc-reform">
    title
</h1>
<p>stuff here</p>

Then you want the adjacent selector:

h1.hc-reform + p{
     clear:both;
}