* Login as root.



   * Move to squid.conf file,

     cd /etc/squid/

     vim squid.conf

  

   * Add the following commmand in acl(access control list),

      acl aclname dstdomain .sitename(for eg, xyzjdfhkjs.com)



   * Then add the condition under the line "INSERT YOUR OWN RULE(S) HERE",

      http_access deny aclname



   For eg,

      acl block-site dstdomain fghsdfkj.com

      http_access deny block-site



   * Finally restart squid,

      /etc/init.d/squid restart