In order to allow Jira to read static content, for example an external .html page, you need to perform the following:
  * Add the following line to the server.xml file:
<code><Context docBase="/atlassian/application-data/jira/data/static-content" path="/static-content" /></code>\\
This line should go after the first <Context></Context> tag under "Catalina" host description.(near the bottom of the file)
  * Download and install the ''Custom Content'' gadget from Atlassian: [[https://marketplace.atlassian.com/plugins/com.tngtech.jira.plugins.customcontent.jira-gadget-custom-content/server/overview|Gadget]]
  * Add the gadget to the dashboard
    * Under the URL put the full URL {URL}/static-content/test.html
    * URL - Deprecated copy the URL above.
  * Save and enjoy the content