Some DevEpxress web controls allow requests to the server to be made via callbacks. This option decides if the response data generated after processing these callbacks ought to be compressed by the server before posting it to the client.
<configuration> ... <devExpress> <compression ... enableCallbackCompression="true" ... /> ... </devExpress> ... </configuration>
You should register the DevExpress Web.config section to apply these settings to your project.
This option is enabled by default. This option's setting is not in effect if the Page HTML Compression option is set to true.