Failed to request data thru port 80

HI, I am a software developer and using Norton Security 2010 in office. I am developing an application to . But there is a problem that my application cannot request data thru port 80 under Norton Security. The data requesting method is just simply pulling thru an URL. It seems the connection is blocked by Norton. May I know is there any checking under port 80? Why the data request from Internet Explorer is fine but failed from application? Thank you.