CSS Only Warning Sign

dabblet.css

@charset "UTF-8"
@import url(http://fonts.googleapis.com/css?family=Droid+Sans|Droid+Sans+Mono);

/** 
 * CSS Only Warning Sign
 * 
 * Live preview available at: http://dabblet.com/gist/6937981 
 * 
 * A lot of website use an icon of a warning sign to display next to important 
 * text. 
 *
 * Making use of the "warning sign" character in the Unicode "Miscellaneous 
 * Symbols" block (the 2600–26FF range) and CSS Only triangles (or "slants" as 
 * we used to call it at the turn of the century) the same effect can be 
 * achieved with just CSS.
 *
 * This is just a simple example using the minimum amount of CSS, it can easily 
 * be expanded to make the sign look more garish. Uhm, I mean pretty.
 * 
 * Further info about the Unicode symbol available at :
 *      http://www.fileformat.info/info/unicode/char/26a0/index.htm
 *
 * Further info about CSS Slants available at :
 *      http://www.infimum.dk/HTML/slantinfo.html
 * 
 * @TODO: Calculate *exact* triangle dimensions:
 *      (border-left-width + border-right-width) * 0.866% = border-bottom-width
 */
.⚠ {
    position: relative; /* So we can position the content as absolute */

    /* Using the borders to create a triangle  */
    border-left: 0.70em solid transparent;
    border-right: 0.70em solid transparent;
    border-bottom: 1.35em solid yellow;

    top: -1em;          /* Correction because of the CSS Triangle trick*/
}
    .⚠::before {
        
        content: "⚠";
        
        /* Position the character over the triangle */
        top: 0.45em;
        left: -0.45em;
        position: absolute;

        color: black;
        font-size: 2em;
        line-height: 1em;
    }


/* Additional style to tart up the page */
html {
	display: table;
	width: 100%;
	min-height: 80%;
}
body {
 	display: table-cell;
	vertical-align: middle;
    background: rgb(205,205,0);
    background: linear-gradient(90deg, rgb(125,125,0), rgb(205,205,0));
    min-height: 80%;
    text-align: center;
}

span {
	font-size: 1500%;
}

/*EOF*/

dabblet.html

<span class="⚠"></span>

dabblet.js

// I can't delete this file or the save to gist feature breaks :-(

settings.json

{"view":"split","fontsize":"100","seethrough":"","prefixfree":"1","page":"result"}

Nice!

For the curious, it looks like this:

I added a live preview here - https://codepen.io/raduamarie/pen/NwQwwM

hope it's ok @Potherca, if it's not, I can delete it. Also changed a bit the borders (there was a bottom white portion)