ESXi does not have WebAccess functionality. It's available through ESX4 and vCenter4.
It can be done with the server or workstation browser plugin. You would need to install server to get the plugin. Do a search in the forums for the method for making the link. It may be somewhere in the forums at http://sanbarrow.com as well. It is also possible to use a VNC viewer to connect directly to the client console. You would need to modify the vmx file to add the vnc entries.
You'll need your ESXi 4.0 host to be managed by vCenter 4.0 to do this.
Here is a script if you manage to get vCenter: generateVMRemoteConsoleURL.pl
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
If you find this information useful, please award points for "correct" or "helpful".