https://www.google.com/webmasters/tools/siteoverview
主要内容有：
分析 robots.txt
查看 robots.txt 文件是否按原样或按修改后的方式拦截特定的网址，并针对不同的 Google 用户代理展开测试。
设置目标地理区域
如果您定位到特定的地理区域中的用户，请将该区域与此网站相关联。
启用增强的图片搜索
在您的网站上启用 Google 的增强型图片搜索技术，包括 Google 托管的高级图片标记技术。
管理网站验证
查看此网站所有已验证的持有人，并选择性地重新验证其中一些人。
设置抓取速度
查看 Google 对您网站抓取频率的统计信息，如果需要，可以选择性地调整抓取速度。
设置首选域名
将首选的域名相联到此网站，以便在 Google 搜索结果中始终显示或从不显示“www.”。
删除网址
从 Google 索引中删除内容，包括加速删除。
Absolute Positioning:
Understanding absolute positioning means understanding the concept of the document flow.
Absolute positioning provides the ability not only to move an element anywhere within the page, but also to remove it from the document flow. An absolutely positioned block no longer influences other elements within the document, and the linear flow continues as if that block doesn't exist.
Relative positioning:
Relative positioning, on the other hand, will not remove an element from the document flow. Based on the element's starting position, a relative position will offset it and then effectively leave a hole behind that other elements must negotiate, as if the element were still positioned there.
A relatively positioned element stays within the document flow; its originating position continues to affect other elements, whereas its new position is ignored by the document flow.
Relative positioning is mostly useful for offsetting elements; an element with a starting position inside a traditional grid may be easily moved outside the grid structure, and elements can be finely adjusted when other positioning options aren't possible. For example, Savarese employs relative positioning to move the dragon at the bottom of the design from a starting point below the white content area, to its final spot at the left of the footer area. Using absolute positioning to position elements near the bottom of a design is much more difficult than positioning them near the top, so this instance of relative positioning makes the adjustment easier.
