In HTML-based Help, topics can open in secondary windows from the Index tab in the viewer. When you add keywords to the index, just link them to secondary windows that you create for the project.
Tip: Design the window first and then follow these steps.
Click the Index tab.
From the drop-down in the upper-left corner, select Index.
Right-click the keyword and select Properties.
Click the Advanced tab (only available with index file keywords).
From Window, select the name of the secondary window.
Topics that reference this keyword will open in the selected window when users select the keyword from the Index tab.
Tip: You can also link keywords to frames that are part of framesets you've created for your project. The Advanced tab includes a Frame drop-down list for selecting frames and linking them to keywords.