3. One or more non-transitory computer-readable media comprising instructions that, when executed with one or more processors, cause a system to at least: provide, to a computing system associated with a user account, a first network-based document of a network-based resource, the first network-based document comprising code and an identifier of a second network-based document of the network-based resource, the identifier comprising a network address of the second network-based document, the code configured at least to, upon execution: determine whether the network address and a cascading style sheets (CSS) attribute of the network address are present in a history stored at the computing system, and determine, based at least in part on presence of the network address and the CSS attribute in the history, that the second network-based document was accessed prior to providing the first network-based document to the computing system, the second network-based document accessed based at least in part on an identifier of the user account; determine an indication that the second network-based document was accessed, the indication determined based at least in part on a determination of the presence of the network address and the CSS attribute in the history upon an execution of the code at the computing system; and authenticate the user account based at least in part on the indication.
3. One or more non-transitory computer-readable media comprising instructions that, when executed with one or more processors, cause a system to at least: provide, to a computing system associated with a user account, a first network-based document of a network-based resource, the first network-based document comprising code and an identifier of a second network-based document of the network-based resource, the identifier comprising a network address of the second network-based document, the code configured at least to, upon execution: determine whether the network address and a cascading style sheets (CSS) attribute of the network address are present in a history stored at the computing system, and determine, based at least in part on presence of the network address and the CSS attribute in the history, that the second network-based document was accessed prior to providing the first network-based document to the computing system, the second network-based document accessed based at least in part on an identifier of the user account; determine an indication that the second network-based document was accessed, the indication determined based at least in part on a determination of the presence of the network address and the CSS attribute in the history upon an execution of the code at the computing system; and authenticate the user account based at least in part on the indication. 10. The one or more non-transitory computer-readable media of claim 3 , wherein the identifier of the second network-based document is inserted in the first network-based document such that, upon rendering the first network-based document at the computing system, the identifier and the second network-based document are not rendered to the user account.