There is just one node for every URL in the website.
But (usually) there are many links pointing to the same URL; all the links pointing to the same URL resolve to the same node, and therefore have the same HTTP status code.
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Googlebot is Google's web crawling bot (sometimes also called a "spider").
Every list provides a different amount of information according to the common usage. When a node in the tree is selected, DRKSpider Java displays contextual information in the right panel.