Firefox: Problem on a Stylesheet

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Visual-Studio

VS2010

browser

In one page in my web project, the map displays well on IE but not does not on Firefox. The MS VS warning message is below:

Unable to edit 'http://js.arcgis.com/3.8/js/esri/css/esri.css'. The stylesheet must be part of the current project and the project must be a Web Site or Web Application.

I use VS 2010. I also tried to load the css locally rather than through internet, but the warning is still the same. How can this problem be solved? Thanks in advance if you can share your experience.
Referring http://forums.asp.net/t/1586914.aspx[^], which points out to make the link like that (adding ?parameter=1):

http://js.arcgis.com/3.8/js/dojo/dijit/themes/claro/claro.css?parameter=1</a>]

But the result is the same.