4. A computer-implemented method comprising: intercepting, at a server including one or more processors, a first request for a source document representing a web page, the first request being transmitted from a computing device to a web server via a network, the first request including web browser information indicating web browser software executing on the computing device; intercepting, at the server, the source document being transmitted from the web server to the computing device via the network in response to the first request, the source document specifying one or more fonts in which to display a text in the source document; rendering, at the server, the web page using the source document, the web page including the text displayed in the one or more fonts; determining, at the server, unique characters displayed at the web page for each of the one or more fonts in which the text is displayed; obtaining, at the server, one or more font subsets based on the unique characters, wherein at least one of the one or more font subsets includes the unique characters in the source document and one or more additional characters related to the unique characters in the source document, and wherein the one or more additional characters related to the unique characters include at least one of (i) one or more characters having a different case than one or more of the unique characters and (ii) one or more characters having a different accent than one or more of the unique characters; and transmitting, from the server, information to the computing device based on whether the web browser software indicated by the web browser information is capable of displaying a font family having a plurality of fonts, the information specifying the one or more font subsets; receiving, at the server, a second request from the computing device, the second request being for one or more missing font subsets from the one or more font subsets specified by the information, the one or more missing font subsets being font subsets that the computing device does not have; embedding, at the server, the one or more missing font subsets in the source document to obtain a modified source document; and transmitting, from the server, the modified source document to the computing device.
4. A computer-implemented method comprising: intercepting, at a server including one or more processors, a first request for a source document representing a web page, the first request being transmitted from a computing device to a web server via a network, the first request including web browser information indicating web browser software executing on the computing device; intercepting, at the server, the source document being transmitted from the web server to the computing device via the network in response to the first request, the source document specifying one or more fonts in which to display a text in the source document; rendering, at the server, the web page using the source document, the web page including the text displayed in the one or more fonts; determining, at the server, unique characters displayed at the web page for each of the one or more fonts in which the text is displayed; obtaining, at the server, one or more font subsets based on the unique characters, wherein at least one of the one or more font subsets includes the unique characters in the source document and one or more additional characters related to the unique characters in the source document, and wherein the one or more additional characters related to the unique characters include at least one of (i) one or more characters having a different case than one or more of the unique characters and (ii) one or more characters having a different accent than one or more of the unique characters; and transmitting, from the server, information to the computing device based on whether the web browser software indicated by the web browser information is capable of displaying a font family having a plurality of fonts, the information specifying the one or more font subsets; receiving, at the server, a second request from the computing device, the second request being for one or more missing font subsets from the one or more font subsets specified by the information, the one or more missing font subsets being font subsets that the computing device does not have; embedding, at the server, the one or more missing font subsets in the source document to obtain a modified source document; and transmitting, from the server, the modified source document to the computing device. 16. The computer-implemented method of claim 4 , further comprising: generating, at the server, the one or more missing font subsets; and transmitting, from the server, the one or more missing font subsets to the computing device.