In HTML exports, there are a few Reporting engine settings that can affect export performance. The first is CopyExternalImages:
This controls whether images from HTTP/HTTPS or FTP sources are linked from their original source or copied (and possibly re-encoded) into the output directory. The default is true; this ensures that reports always have the same image. Set to false if the image is dynamically generated, in which case you'd want to display the most recent view.
The Style and ForceBufferedWriting settings control how stylesheets are produced and whether the generated HTML output will be held in a buffer until the report processing is finished:
Style information can be stored inline, or in the <head> element of the generated HTML file:
Or in an external CSS file:
ForceBufferedWriting should be set to true if a report uses an external CSS file. Browsers request all resources they find in the HTML stream, so if a browser requests a style sheet that has not yet been fully generated, the report cannot display correctly. It is safe to disable buffering if the styles are inline because the browser will not need to fetch an external style sheet in that case. Buffered content will appear slower to the user than non-buffered content because browsers render partial HTML pages while data is still being received from the server. Buffering will delay that rendering until the report is fully processed on the server.