If you have a custom theme you need really need to save the code from the standard theme stylesheet to the custom one.
/* --------------------------------------------------------------
Basic WordPress Blog Styles
-------------------------------------------------------------- */
/* Images
-------------------------------------------------------------- */
.entry-content img {
margin: 0 0 1.5em 0;
}
.alignleft,
img.alignleft {
display: inline;
float: left;
margin-right: 1.5em;
}
.alignright,
img.alignright {
display: inline;
float: right;
margin-left: 1.5em;
}
.aligncenter,
img.aligncenter {
clear: both;
display: block;
margin-left: auto;
margin-right: auto;
}
.wp-caption {
text-align: center;
margin-bottom: 1.5em;
}
.wp-caption img {
border: 0 none;
margin: 0;
padding: 0;
}
.wp-caption p.wp-caption-text {
margin: 0;
}
.wp-smiley {
max-height: 1em;
margin:0 !important;
}
.gallery dl {
margin: 0;
}
.gallery-caption {
margin:-1.5em 0 0 0;
}
/* Pullquotes
-------------------------------------------------------------- */
blockquote.left {
float: left;
margin-left: 0;
margin-right: 20px;
text-align: right;
width: 33%;
}
blockquote.right {
float: right;
margin-left: 20px;
margin-right: 0;
text-align: left;
width: 33%;
}