Create a browser object for display of a html page, when creation is complete the call handle
will return a HTML_BrowserReady_t callback for the HHTMLBrowser of your new browser.
The user agent string is a substring to be added to the general user agent string so you can
identify your client on web servers.
The userCSS string lets you apply a CSS style sheet to every displayed page, leave null if
you do not require this functionality.
YOU MUST HAVE IMPLEMENTED HANDLERS FOR HTML_BrowserReady_t, HTML_StartRequest_t,
HTML_JSAlert_t, HTML_JSConfirm_t, and HTML_FileOpenDialog_t! See the CALLBACKS
section of this interface (AllowStartRequest, etc) for more details. If you do
not implement these callback handlers, the browser may appear to hang instead of
navigating to new pages or triggering javascript popups.