新手如何更换自己喜欢的背景以及此背景的css码

以下内容为转载（对于css码可以自己写当然也可以去网上搜现成的）：

更换背景教学：https://jingyan.baidu.com/album/fc07f9897c730412ffe519c0.html

此背景的css码：（博客皮肤选择darkgreentrip即可）

#home {
margin: 0 auto;
width: 80%;/*原始65*/
min-width: 980px;/*页面顶部的宽度*/
background-color: rgba(245, 245, 245, 0.7);
padding: 30px;
margin-top: 50px;
margin-bottom: 50px;
box-shadow: 0 2px 6px rgba(100, 100, 100, 0.3);
}
body {
background: rgba(12, 100, 129, 1) url('http://images.cnblogs.com/cnblogs_com/Penn000/1013849/o_123.jpg') fixed no-repeat;
background-position: 50% 5%; 
background-size: cover;
}
#blogTitle {
height: 100px; /*高度*/
clear: both;
background-color: rgba(245, 245, 245, 0);
}
#blogTitle h1 {
font-size: 36px;
font-weight: bold;
line-height: 1.8em;/*原始 1.6em*/
margin-top: 10px;/*原始 15px */
color: #548B54;
}
#blogTitle h2 {
font-weight: normal;
font-size: 17px;/*原始 16px ；font-size: 1.0rem;*/ 
line-height: 1.8;
color: #111;
font-weight: bold;
text-align: right;
float: right; 
}
#navigator{
background-color: rgba(33, 160, 139, 0.9);
}
#navList a:link, #navList a:visited, #navList a:active{
color: #eee;
font-size: 18px;
font-weight: bold;
}
.blogStats{
color: #eee;
}
.postTitle {
border-left: 8px solid rgba(33, 160, 139, 0.68);
margin-left: 10px;
margin-bottom: 10px;
font-size: 20px;
float: right;
width: 100%;
clear: both;
}
.postTitle a:link, .postTitle a:visited, .postTitle a:active {
color: #21759b;
transition: all 0.4s linear 0s;
}
.postTitle a:hover {
margin-left: 30px;
color: #0f3647;
text-decoration: none;
}
.postCon {
float: right;
line-height: 1.5em;
width: 100%;
clear: both;
padding: 10px 0;
}

.day .postTitle a {
padding-left: 10px;
}
.day {
background: rgba(255, 255, 255, 0.5);
}
/*文章附加信息*/
.postDesc { 
background: url(images/posted_time.png) no-repeat 0 1px;
color: #757575;
float: left;
width: 100%;
clear: both;
text-align: left; 
font-family: "微软雅黑" , "宋体" , "黑体" ,Arial;
font-size: 13px;
padding-right: 20px;/*5px padding-left: 90px;posted 发表时间左边距离*/
margin-top: 20px;
line-height: 1.8;
padding-bottom: 35px;
}

.newsItem, .catListEssay, .catListLink, .catListNoteBook, .catListTag, .catListPostCategory, 
.catListPostArchive, .catListImageCategory, .catListArticleArchive, .catListView, 
.catListFeedback, .mySearch, .catListComment, .catListBlogRank, .catList, .catListArticleCategory ,#blog-calendar
{
background: rgba(255, 255, 255, 0.5);
margin-bottom: 35px;
word-wrap: break-word;
}

.CalTitle{
background: rgba(255, 255, 255, 0);
}
.catListTitle{
background-color: rgba(33, 160, 139, 0.9);
}

#topics{
background: rgba(255, 255, 255, 0.5);
}

.c_ad_block{
display: none;
}

#tbCommentBody{
width: 100%;
height: 200px;
background: rgba(255, 255, 255, 0.5);
}

#q{background: rgba(255, 255, 255, 0);}

.CalNextPrev{background: rgba(255, 255, 255, 0);}

.cnblogs_code{
background: rgba(255, 255, 255, 0); 
}

.cnblogs_code div{
background: rgba(255, 255, 255, 0); 
}

.cnblogs_code_toolbar{
background: rgba(255, 255, 255, 0); 
}

.entrylist{
background: rgba(255, 255, 255, 0.5); 
}