i get an error 403 when trying to access american express site

If you are using Safari, from the menu bar click Safari / Preferences then select the Security tab. Click: Show Cookies. Delete all AMEX related cookies.

Restart your Mac, then launch Safari.

If that doesn't help, go back to Safari / Preferences then select the Advanced tab. Click the Change Settings button next to: Proxies.

That will prompt the System Preferences / Network - Proxies pane. If any of the boxes on the left are checked, deselect the box(es) then click OK.

Quit then relaunch Safari. Try the AMEX site.

We are assuming you are using a Mac because you posted to the Macbook forum. If you are using an iPad, open the Settings App, and select Safari, and change the Accept Cookies section. Mind you, if you are on an open WiFi network (Airport network), or 3G network I do not recommend entering any Amex data as neither is secure. You should at minimum be on a WPA2 secured network or ethernet based network to an internet service provider to your Mac or PC. Any network that doesn't have a password, is not secure, albeit the automatic login feature if it was set with a WPA2 network is secure as long as it is a connection you manage. If it is a WiFi hotspot, it is not secure.