NewWebWindow::WebFile [directory_of_the_file] [teh_file] [output_var]

directory_of_the_file: The directory wich have the web file.
teh_file: The local file to open in another Browser Window.
output_var: The var to output that path of the local web browser.

NewWebWindow::WebUrl [dummy_directory_of_a_html_file] [dummy_HTML_file] [teh_URL] [output_var]

dummy_directory_of_a_html_file: a dummy directory of a local web file.
dummy_HTML_file: A local dummy web file.
teh_URL: The URL to open in another Window.
output_var: The var to output that path of the local web browser.

The "dummy_directory_of_a_html_file" & "dummy_HTML_file" is for detecting the default 
Web Browser. If you don't need the dummy_HTML_file, you might want to extract it 
in your PLUGINSDIR, after installation the dummy_HTML_file should be deleted.

See examples "WebFile.nsi" & "WebUrl.nsi"