CSS Opera (left)

#un-button.un-left.css3 {
border: 1px solid #c96300;
left:-6px;
top:50%;
-webkit-transform: rotate(-90deg);
-moz-transform: rotate(-90deg);
-ms-transform: rotate(-90deg);
-o-transform: rotate(-90deg);
transform: rotate(-90deg);

transform-origin:0 0 0;
-webkit-transform-origin:0 0 0;
-moz-transform-origin:0 0 0;
-ms-transform-origin:0 0 0;
-o-transform-origin: 0 0 0;
}

#un-button,#un-button:hover {
outline:medium none!important;
}

#un-button {
position:fixed;

opacity:0.9;
-webkit-opacity: 0.9;
-moz-opacity: 0.9;
filter:alpha(opacity=90)

z-index:9997;

text-decoration:none;
color:#fff;

-webkit-border-radius: 6px;
-moz-border-radius: 6px;
border-radius: 6px;

background-color:#e48700;
font-size:16px;
float:none;

text-shadow:none;
-moz-text-shadow: none;
-webkit-text-shadow: none;
-ms-filter: "progid:DXImageTransform.Microsoft.Shadow(Strength=0, Direction=0, Color='#ffffff')";

padding:15px 15px 15px 15px;
}

#un-button:hover {
background-color:#c87602;
}

    <a id="un-button" class="un-left css3" href="#" style="left: -6px;"
       data-toggle="modal"
       data-target="#contactsModal">
      <span class="glyphicon glyphicon-info-sign"></span>&nbsp;&nbsp;&nbsp;
        {% trans "Обратная связь" %}
    </a>