From my asp.net website, I export data into excel using Microsoft ReportViewer. When I open the excel I get the following error

When I export few rows of data, it works fine. But when I export some what huge data, it throws this error. Can some one provide some help?
The data you are exporting is referencing css files on the webserver.
once you are downloading the file, you are downloading those references.
When you open the file, it’s trying to open the css file’s locally, but they do not exist locally.
I would either download the css files separately, and place them in the local location they should exist in, or prevent your export from referencing the files in whichever line has the references. (probably near the top)