Yammer Fluid App Userstyle.

gistfile1.css

body,
div.page-content.two-column-layout,
div.page-content.three-column-layout {
    background: none !important;
}

/* Hide the chat window. */
#yj-yam.ui.chat.ChatManager {
  display: none;
}

.two-column-layout #column-two {
    margin-top: 0px;
}

div#column-two {
    padding: 5px 0 0 30px !important;
}

div.page-header,
div.yj-feed-title-container,
#column-three,
#column-one,
#footer {
    display: none !important;
}

div.yj-avatar img {
    border-radius: 3px;
    box-shadow: 3px 3px 1px #888;
}

body div#uni-header-wrapper,
#uni-header {
    width: auto !important;
    min-width: 0;
}

#uni-left-content {
    width: 205px;
}

#uni-left-content #uni-search {
    width: 100px !important;
}

#uni-logo,
#uni-search-glass {
    display: none;
}

#uni-left-content #uni-search input {
    width: 80px !important;
}

body #uni-user-menus-container {
    display: block;
    float: left !important;
    width: 310px !important;
}

body div.two-column-layout {
    clear: both;
    float: left;
    width:  500px !important;
    background: pink !important;
    overflow: visible;
    margin: 0;
    padding: 0;
}

div#column-two {
    width: 500px !important;
    padding: 0 5px !important;
    margin: 0;
    float: left;
    padding-left: 4px !important;
}

div.yj-thread-replies-container {
    margin: 0;
}