request username and password

Dear experts,

hope all of you can guide me in this problem...

my user have uploaded power point file in KM. the power point file contain hyperlink to html file also in the same KM. user opened the file and when the user click the hyperlink, the portal server request username and password before open the html file. my user do not want enter the username and password again, once the user already logon to the KM. can anybody give me steps or suggestion on this problem?

help me,

faeza