1. An electronic device, comprising: a display; one or more processors; memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for: displaying at least a portion of an electronic document at a first magnification level on the display; detecting a first input indicating a first insertion point in the document, wherein the first insertion point is proximate to a first portion of text in the document; in response to detecting the first input: selecting a second magnification level different from the first magnification level, wherein the second magnification level is selected so as to display the first portion of text at a default target text display size; and displaying a portion of the document at the second magnification level; detecting a second input corresponding to a request to display a portion of the document at a third magnification level different from the second magnification level; in response to detecting the second input: displaying the portion of the document at the third magnification level; and storing a user-adjusted target text display size corresponding to a text display size of the first portion of text at the third magnification level, wherein the user-adjusted target text display size is different from the default target text display size; and after storing the user-adjusted target text display size: detecting a third input indicating a second insertion point in the document, wherein the second insertion point is proximate to a second portion of text in the document; and in response to detecting the third input, displaying the document at a respective magnification level such that the second portion of text is displayed at the user-adjusted target text display size.
6. The device of claim 1 , wherein the respective magnification level is different from the third magnification level if the second portion of text has a different font size from a font size of the first portion of text.