how to fix the issue asking username and password in some browsers like Firefox and opera etc?

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SSRS

Hi All ,


i designed and developed 10 reports in ssrs 2008 r2 . in all reports i am trying to pass the parameters in URL itself and finally i am exporting it into excel file
for example

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


the above URL is working fine i.e after clicking the above URL it is showing one download window with options open save and cancel buttons.
the above URL is working in IE and Chrome very well.

Note: for some systems the above url is not working in IE and Chrome also

but coming to mozilla firefox and opera and other browsers it is asking username and password.

i studied some websites but they also not giving proper methods

http://support.mozilla.com/en-US/kb/Firefox+asks+for+user+name+and+password+on+internal+sites

how can i over come this problem its very urgent to me.
coming to mozilla we can do like
1.about:config
2.network url we can add our server url.

but the above concept is also not good because for all clients we cannot ask them to do the above 2 steps in mozilla firefox.

its very urgent and if any one have ideal please try to give step by step solution

simple to say about my requiremtn in one word, the above url should work in all browsers and in all systems without asking username and password

regards,

Franklin