[css] What does the "+" (plus sign) CSS selector mean?

For example:

p + p {
  /* Some declarations */
}

I don't know what the + means. What's the difference between this and just defining a style for p without + p?

It selects the next paragraph and indents the beginning of the paragraph from the left just as you might in Microsoft Word.

"+" is the adjacent sibling selector. It will select any p DIRECTLY AFTER a p (not a child or parent though, a sibling).

It would match any element p that's immediately adjacent to an element 'p'. See: http://www.w3.org/TR/CSS2/selector.html

The + selector targets the one element after. On a similar note, the ~ selector targets all the elements after. Here's a diagram, if you're confused:

It means it matches to every p element which is immediately adjacent

www.snoopcode.com/css/examples/css-adjacent-sibling-selector

The Plus (+) will select the first immediate element. When you use + selector you have to give two parameters. This will be more clear by example: here div and span are parameters, so in this case only first span after the div will be styled.

 div+ span{
   color: green;
   padding :100px;
}

     <div>The top or first element  </div>
       <span >this is span immediately after div, this will be selected</span>
       <span>This will not be selected</span>

Above style will only apply to first span after div. It is important to note that second span will not be selected.

p+p{
//styling the code
}

p+p{
} simply mean find all the adjacent/sibling paragraphs with respect to first paragraph in DOM body.

    <div>
    <input type="text" placeholder="something">
    <p>This is first paragraph</p>
    <button>Button </button>
    <p> This is second paragraph</p>
    <p>This is third paragraph</p>
    </div>

    Styling part 
    <style type="text/css">
        p+p{
            color: red;
            font-weight: bolder;
        }
    </style>

   It will style all sibling paragraph with red color.

final output look like this

The + sign means select an "adjacent sibling"

For example, this style will apply from the second <p>:

p + p {
   font-weight: bold;
} 

<div>
   <p>Paragraph 1</p>
   <p>Paragraph 2</p>
</div>

Example

See this JSFiddle and you will understand it: http://jsfiddle.net/7c05m7tv/ (Another JSFiddle: http://jsfiddle.net/7c05m7tv/70/)

Browser Support

Adjacent sibling selectors are supported in all modern browsers.

Learn more

• http://css-tricks.com/almanac/selectors/a/adjacent-sibling/
• http://www.w3.org/TR/CSS2/selector.html#adjacent-selectors
• https://developer.mozilla.org/en-US/docs/Web/CSS/Adjacent_sibling_selectors

It's the Adjacent sibling selector.

From Splash of Style blog.

To define a CSS adjacent selector, the plus sign is used.

h1+p {color:blue;}

The above CSS code will format the first paragraph after (not inside) any h1 headings as blue.

h1>p selects any p element that is a direct (first generation) child (inside) of an h1 element.

• h1>p matches <h1> <p></p> </h1> (<p> inside <h1>)

h1+p will select the first p element that is a sibling (at the same level of the dom) as an h1 element.

• h1+p matches <h1></h1> <p><p/> (<p> next to/after <h1>)

+ presents one of the relative selectors. Here is a list of all relative selectors:

div p - All <p> elements inside of a <div> element are selected.

div > p - All <p> elements whose direct parent is <div> are selected. It works backwards too (p < div)

div + p - All <p> elements placed immediately after a <div> element are selected.

div ~ p - All <p> elements that are preceded by a <div> element are selected.

Here is some more about selectors.

+ selector is called Adjacent Sibling Selector.

For example, the selector p + p, selects the p elements immediately following the p elements

It can be thought of as a looking outside selector which checks for the immediately following element.

Here is a sample snippet to make things more clear:

body {_x000D_
  font-family: Tahoma;_x000D_
  font-size: 12px;_x000D_
}_x000D_
p + p {_x000D_
  margin-left: 10px;_x000D_
}

<div>_x000D_
  <p>Header paragraph</p>_x000D_
  <p>This is a paragraph</p>_x000D_
  <p>This is another paragraph</p>_x000D_
  <p>This is yet another paragraph</p>_x000D_
  <hr>_x000D_
  <p>Footer paragraph</p>_x000D_
</div>

Since we are one the same topic, it is worth mentioning another selector, ~ selector, which is General Sibling Selector

For example, p ~ p selects all the p which follows the p doesn't matter where it is, but both p should be having the same parent.

Here is how it looks like with the same markup:

body {_x000D_
  font-family: Tahoma;_x000D_
  font-size: 12px;_x000D_
}_x000D_
p ~ p {_x000D_
  margin-left: 10px;_x000D_
}

<div>_x000D_
  <p>Header paragraph</p>_x000D_
  <p>This is a paragraph</p>_x000D_
  <p>This is another paragraph</p>_x000D_
  <p>This is yet another paragraph</p>_x000D_
  <hr>_x000D_
  <p>Footer paragraph</p>_x000D_
</div>

Notice that the last p is also matched in this sample.