Why will my Windows 95/98 login but will not load a webpage?

Set up may be incorrect , check:

Winipcfg will tell you if your IP stack is working correctly. The router will assign an IP address if you are connected correctly. Below is what you should see if the connection is good and and the IP stack is working correctly. This can be done by clicking on Start > Run and typing winipcfg in the blank field.

Check to see if your computer is getting an IP Address , Subnet Address and Gateway
(they will be different than the picture above)

Also a DNS server needs to be asigned.

If not go back to your dialup setting and make sure your set on PPP
and NetBEUI, IPX/SPX are turned off