blockquooooooooote magic

.post blockquote {
    margin-left: 0;
    border-left: 2px solid #333;
    padding-left: 10px;
}
.post blockquote blockquote {
    border-left: 2px solid #666;
}
.post blockquote blockquote blockquote {
    border-left: 2px solid #999;
}
.post blockquote blockquote blockquote blockquote {
    border-left: 2px solid #bbb;
}
.post blockquote blockquote blockquote blockquote blockquote {
    border-left: 2px solid #ddd;
}

5段階までグラデーションblockquote

dombdombdomb - blockquooooooooote