I found why this error is happening. the sarg_reports.php is looking for the index.html file in sarg-reports/index.html, which is not there. Basically the default installation of sarg in Fedora and Centos is giving us a "report" directory format like the following. /var/www/html/reports/index.html. This index.html is generated when using "sarg -x " command ,which contains all the report details.
But in PfSense Sarg ,the directory structure is little-bit different. I dont know why and how to solve this.If you are placing one index.html file in "/usr/local/www/sarg-reports/" ,the webconfigurator will show that "index.html" while taking "Status->sarg Reports-> View Reports".
The directory structure of Sarg in Pfsense is as this "sarg-reports/"year"/"month"/"date"/index.html"( Actual Sarg directory structure "sarg-reports/index.html" + lot of directory in "yyyy-mm-dd"). The configuration of this sarg_reports.php is given in sarg_frame.php,where the path of report file is given.
I am struck with this error ..Can any one give further tips in the topic............!!!