Configuring cookies for MS Internet Explorer
For configuration see MS Internet Explorer | Tools | Internet Options | card Privacy | button Advanced | tick these boxes
• Override automatic cookie handling
• Accept for item First-party Cookies
• Accept for item Third-party Cookies
• Always allow session cookies
  ... view configuration

Not functioning cookies for the given setting under MS Internet Explorer
If cookies are not functioning under MS Internet Explorer 6 for the described configuration check the cookies configuration for the particular server:

For configuration see MS Internet Explorer | Tools | Internet Options | card Privacy | button Sites | list Managed websites | check if the bvv.cz domain appears on the list and if it does set the Always Allow value
  ... view configuration

Not functioning cookies
If cookies are still not functioning despite correct configuration contact the administrator of your computer and your network. It is necessary to check and possibly enable for filtering cookies in other settings (e.g. personal firewall, company firewall, proxy server etc.).