Box with a triangle like a chat

Here's the same output with :after property :

HTML

<p>
  Hello!!!
</p>

CSS

p {
  display:inline-block;
  padding:5px 6px 8px 6px;
  border-radius: 6px;
  float: right;
  margin-right: 40px;
  color:black;
  background-color:#146f79;
  position: relative;
}

p:after {
  content: "";
  position:absolute;
  margin-top:-6px;
  margin-left:-5px;
  border-left: 12px solid transparent;
  border-right: 12px solid transparent;
  border-bottom: 12px solid #146f79;
  transform:rotate(-45deg);
  right: -15px; 
  top: 10px;
}

Fiddle


i think this site help you : https://css-tricks.com/examples/ShapesOfCSS/

#talkbubble { width: 120px; height: 80px; background: red; position: relative; -moz-border-radius: 10px; -webkit-border-radius: 10px; border-radius: 10px; }

#talkbubble:before { content:""; position: absolute; left: 100%; top: 26px; width: 0; height: 0; border-top: 13px solid transparent; border-left: 26px solid red; border-bottom: 13px solid transparent; }
<div id="talkbubble"></div>


Kadriles is right, but I already made simple example without any negative margin or box sizes

.bubble {
  position: absolute;
  background: slategray;
  color: white;
  padding: 6px 10px;
  border-radius: 5px 0 5px 5px;
}

.bubble:after {
  content: '';
  position: absolute;
  left: 100%;
  top: 0;
  border-top: 8px solid slategray;
  border-right: 12px solid transparent;
}
<div class="bubble">Hello</div>