BACKGROUND [0001] The Internet and the World Wide Web (the web) are becoming an integral part of our daily lives, being used for work, entertainment, research, and so on. Oftentimes, users create a list of favorite or bookmarked web pages that they access frequently. These web pages can be easily re-accessed by the user by selecting them from the list. However, these web pages can change over time. Typically, in order for the user to monitor changes to the web pages, he or she needs to manually re-access the web pages to see if there are any changes. Such re-accessing can be time consuming and burdensome on the user. Other techniques that allow users to monitor changes to the web pages include having the servers hosting the web pages email notifications of changes to the user, or having the servers hosting the web pages install desktop plug-ins on the user's computer that monitor the content on the web pages. However, such techniques require a significant amount of work on the part of the developers of and/or servers hosting the web pages, and typically provide the user with a different experience for each web page. Accordingly, it would be beneficial to have an improved way for notifying users of changes to web pages. SUMMARY [0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. |0003| In accordance with one or more aspects of managing web page links using structured data, requests to collect structured data in a web page and to subscribe to that structured data are received. This structured data is stored in a data store to allow offline use of the structured data. |0004] In accordance with one or more other aspects of managing web page links using structured data, a computing device displays multiple links each of which identifies a different one of multiple web pages. Additionally, the multiple pages include structured data. The display of these multiple links is altered as the computing device detects changes to the structured data in the web pages. (0005] In accordance with one or more other aspects of managing web page links using structured data, a web page includes structured data that has been subscribed to. A computing device detects changes to the web page, and notifies a user of a change to the web page only if the change is a change to the structured data and not a change to other portions of the web page. BRIEF DESCRIPTION OF THE DRAWINGS [0006] The same numbers are used throughout the drawings to reference like features. [0007] Fig. 1 illustrates an example system in which the managing web page links using structured data can be used in accordance one or more embodiments. [0008] Fig. 2 illustrates an example web page that includes structured data in accordance with one or more embodiments. [0009] Fig. 3 is a flowchart illustrating an example process for collecting and subscribing to structured data in accordance with one or more embodiments. [0010] Fig. 4 illustrates an example user interface allowing structured data to be collected and subscribed to in accordance with one or more embodiments. [0011] Fig. 5 is a flowchart illustrating an example process for synchronizing structured data in accordance with one or more embodiments. ]0012] Fig. 6 is a flowchart illustrating an example process for performing at least some link management using structured data in accordance with one or more embodiments. [0013] Fig. 7 illustrates an example user interface illustrating a favorites list in accordance with one or more embodiments. [0014] Fig. 8 illustrates another example user interface illustrating a favorites list in accordance with one or more embodiments. [0015] Fig. 9 illustrates an example computing device that can be configured to implement the managing web page links using structured data in accordance with one or more embodiments. DETAILED DESCRIPTION [0016] Managing web page links using structured data is discussed herein. Users can select structured data to be collected from different web pages and have the web pages that include that structured data stored for offline use. Additionally, the user can subscribe to changes to the structured data, so that whenever the structured data is changed the user is notified of the change. A user interface notifies the user of changes to the structured data, and further allows the user to preview those changes prior to the user navigating to the web page. [0017] Fig. 1 illustrates an example system 100 in which the managing web page links using structured data can be used. System 100 includes a computing device 102 having a web browser 104, a synchronization engine 106, and a data store 108. Computing device 102 accesses web pages 110 over a network 112. Computing device 102 can be any of a variety of different computing devices, such as a desktop computer, handheld computer, laptop computer, server computer, automotive computer, cell phone, personal digital assistant (PDA), game console, and so forth. Browser 104 allows computing device 102 to retrieve, via network 112, web pages 110 and display the retrieved web pages to a user(s) of device 102. Network 112 can be any of a variety of networks, including the Internet, a local area network, other public and/or proprietary networks, combinations thereof, and so forth. (0018) One or more web pages 110 can each include one or more pieces of structured data 114. Structured data 114 is data that is in a format that is known by and expected by a consumer of the data. Structured data 114 can be formatted in accordance with known structured data standards, such as the Extensible Markup Language (XML) or HyperText Markup Language (HTML) formats. Alternatively, structured data 114 can be formatted in accordance with other public and/or proprietary standards. Whatever format is used for structured data 114, this format is known by consumers of data 114 so that data 114 can be used by such consumers, as discussed in more detail below. The amount and kind of data that constitutes a piece of structured data can vary, and is defined as part of a data type. [0019] Different pieces of structured data 114 can be of different data types, also referred to as structured data types. A variety of different data types can be used, such as a contact type, an event type, a calendar type, a product type, a picture type, a music type, a trip type, a web page type, a geographic location type, and so forth. A data type can be defined to include any kind of data in different properties or fields, such as a date, a time, mapping coordinates, a name, a phone number, an address, a product description, a destination name, a price, and so forth. Additionally, in certain embodiments an entire page 110 can be treated as a type of structured data. [0020] The structured data type of a particular piece of structured data can be identified in different manners. In certain embodiments, the structured data itself indicates the data type. For example, different HTML tags can be used to identify different structured data types, or a property or parameter of the structured data itself may identify the structured data type. Alternately or additionally, the structured data can be identified in different manners, such as by using header information in the page 110, or other meta data in page 110 or associated with page 110. [0021] The structured data itself can be, but need not be, displayed to the user as part of the web page. For example, if the structured data includes various properties (e.g., the date, time, and geographic location for an event (such as a speech)), then the web page may display these properties in various parts of the web page using HTML code that is separate from the structured data. In such situations, the structured data is included in the HTML of the web page but is not displayed to the user. Alternatively, the structured data can be displayed to the user. In one or more embodiments, the structured data is displayed as part of the web page. [0022] Additionally or alternatively, browser 104 can use the structured data in the web page to generate and display a preview of the structured data. A preview can be, for example, a window overlaying the web page that is opened when the user hovers a pointer over or near an indicator of the presence of structured data using a cursor control device (e.g., keeping the pointer within a particular distance of the indicator) for at least a threshold amount of time. This preview is generated at computing device 102; the developer of the web page need not have any knowledge of when or whether the preview is displayed. Alternatively, the developer of the web page may identify, such as within the structured data itself, which parts of the structured data should be displayed as part of the preview. [0023] Fig. 2 illustrates an example web page 200 that includes structured data in accordance with one or more embodiments. Web page 200 includes a calendar event 202 as well as additional text 204 and images 206. In this particular instance, calendar event 202 has three fields or properties - a location field and two date fields. These fields are described in the page's HTML 208 by, for example, suitable HTML tags such as the illustrated