If I use key like

web.page.get[www.zabbix.com,/partner_program]

it does not work for some my web servers.
While this one does work:

web.page.get[www.zabbix.com,partner_program]

The reason is that zabbix agent adds one heading slash / to 2nd key param unconditionally, which I personally would consider as a bug.
In the result some my web servers do not proceed double slash // in URL and return HTTP 404.

Why bug - in documentation it's specified that defaults for 2nd param is /, but I specify a value for 2nd param, so, according to general zabbix logic, defaults should not affect in any way.

I'm not sure that it will be fixed in agent's code, so documentation should explicitly mention the behavior.