Required library edition:
Required library file: dhtmlxtabbar.js

sets the content of the tab as the href to an external file

• id - the tab id
• href - the URL of the page that will be opened in the tab

tabbar = new dhtmlXTabBar("a_tabbar", "top");
tabbar.setHrefMode("iframes-on-demand");
...
tabbar.addTab("a1", "Docs", "100px");
tabbar.addTab("a2", "Samples", "100px");
 
tabbar.setContentHref("a1", "http://docs.dhtmlx.com/doku.php?id=dhtmlxtabbar:toc");
tabbar.setContentHref("a2", "http://www.dhtmlx.com/docs/products/dhtmlxTabbar/samples/");

See also: setContentHTML, setContent, setHrefMode, forceLoad

Some extra info, about accessing the loaded content, can be checked at Access iframe content article