After posting images on my forum using the image tag, images were cut off, and resizing browser would cut them off even more.

So I added...

.text-area img {
  max-width: 100%;
  height: auto;
}

After

.text-area blockquote,
.postmsg pre {
    border: 0;
    font-style: normal;
    font-weight: normal;
    margin: 0;
    padding: 0;
}

Images are not cut off and shrink and expand with resizing browser. More mobile friendly.