1. One or more computer-readable media having computer-executable instructions embodied thereon for performing a method of identifying a designated portion of a web page after the web page has been updated, the method comprising: receiving, at a computing device, a selection of a first subsection of the web page; retrieving and storing, at the computing device, a first version of the web page; after a threshold time period, retrieving, from a server hosting the web page, a second version of the web page; generating, at the computing device, a first condensed document-object-model (“DOM”) tree based on the first version of the web page by removing qualifying nodes from a full DOM tree based on the first version of the web page; generating, at the computing device, a second condensed DOM tree based on the second version of the web page by removing qualifying nodes from a full version DOM tree based on the second version of the web page; comparing the first condensed DOM tree to the second condensed DOM tree with a low cost edit algorithm to identify one or more sub-trees that are identical in both the first condensed DOM tree and the second condensed DOM tree such that the one or more sub-trees that are identical are excluded from a node distance calculation of the first condensed DOM tree; calculating using a tree distance algorithm a node distance metric between each nonexcluded sub-tree within the first sub-tree of the first condensed DOM tree and one or more nonexcluded sub-trees within the second condensed DOM tree, wherein the node distance metric increases as an amount of differences between sub-trees increases; identifying, at the computing device, a second subsection within the second version of the web page that corresponds to the first subsection using the first condensed DOM tree and the second condensed DOM tree; updating an aggregate website, based on the second subsection within the second version of the web page that corresponds to the first subsection within the first version of the web page.