CSS :first-letter not working

You can get the intended behavior by setting the span's display property to inline-block:

.heading span {
  display: inline-block;
}

.heading span:first-letter {
  color: red;
}

<div class="heading">
  <span>An</span>
  <span>Interesting</span>
  <span>Heading</span>
</div>

::first-letter does not work on inline elements such as a span. ::first-letter works on block elements such as a paragraph, table caption, table cell, list item, or those with their display property set to inline-block.

Therefore it's better to apply ::first-letter to a p instead of a span.

p::first-letter {font-size: 500px;}

or if you want a ::first-letter selector in a span then write it like this:

p b span::first-letter {font-size: 500px !important;}
span {display:block}

MDN provides the rationale for this non-obvious behaviour:

The ::first-letter CSS pseudo-element selects the first letter of the first line of a block, if it is not preceded by any other content (such as images or inline tables) on its line.

...

A first line has only meaning in a block-container box, therefore the ::first-letter pseudo-element has only an effect on elements with a display value of block, inline-block, table-cell, list-item or table-caption. In all other cases, ::first-letter has no effect.

Another odd case(apart from not working on inline items) is if you use :before the :first-letter will apply to the before not the actual first letter see codepen

Examples

• http://jsfiddle.net/sandeep/KvGr2/9/
• http://krijnhoetmer.nl/stuff/css/first-letter-inline-block/

References

https://developer.mozilla.org/en-US/docs/Web/CSS/::first-letter http://reference.sitepoint.com/css/pseudoelement-firstletter