the css style of flask web development:development web applications with python

i am a new hand，i play in the book，but in the eleventh capter appear the css style problem。enter image description here

so i download the author code and copy the style.css and _posts.html to my project but it cant be solved。this is copy of css.style and _posts.html

.profile-thumbnail {
    position: absolute;
}
.profile-header {
    min-height: 260px;
    margin-left: 280px;
}
ul.posts {
    list-style-type: none;
    padding: 0px;
    margin: 16px 0px 0px 0px;
    border-top: 1px solid #e0e0e0;
}
ul.posts li.post {
    padding: 8px;
    border-bottom: 1px solid #e0e0e0;
}
ul.posts li.post:hover {
    background-color: #f0f0f0;
}
div.post-date {
    float: right;
}
div.post-author {
    font-weight: bold;
}
div.post-thumbnail {
    position: absolute;
}
div.post-content {
    margin-left: 48px;
    min-height: 48px;
}
div.pagination {
    width: 100%;
    text-align: right;
    padding: 0px;
    margin: 0px;
}

<ul class="posts">
    
</ul>