SSRS 2008 R2 deployment issues in mozilla firefox browser?

Hi ,

i developed and deployed one report in ssrs2008 r2.

i can able to use my URL in IE and Google Chrome.

but when ever i use my report URL in mozilla firefox then it is asking username and password.

sample URL is 

http://localhost:8080/ReportServer/Pages/ReportViewer.aspx?%2fReport+Project1%2fReport1&rs:Command=Render&rs:Format=excel

how can fix this issue.

thanks in advance

sai