17. A non-transitory computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by an electronic device with a display, cause the device to: display at least a portion of an electronic document at a first magnification level on the display; detect 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: select 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 display a portion of the document at the second magnification level; detect 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: display the portion of the document at the third magnification level; and store 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: detect 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, display the document at a respective magnification level such that the second portion of text is displayed at the user-adjusted target text display size.
20. The computer readable storage medium of claim 17 , wherein the default target text display size is a predefined value in the range 10 pt-24 pt.