路径
1. 相对路径
- 是从代码所在的文件出发，去寻找我们的目标文件，我们所说的上一级，同一级，下一级，就是图片位于html页面的位置
- ../上一级，../../上两级，以此类推
2. 绝对路径
When nothing seems to help, I go look at a stonecutter hammering away at his rock, perhaps a hundred times without as much as a crack showing in it. Yet at the hundred and first blow it will split in two, and I know it was not that blow that did it, but all that had gone before. -- Jacob Riis
