How do I always open a link in a new HTML window?
This solution is deprecated and should be avoided when creating standards-compliant or accessible websites.
At the top of your document you can specify <base target="_blank">.
The correct target for new windows is _blank (when authoring with a Frameset-inclusive document type definition). In practice case-sensitivity is significant for this value. However, the specification says that target names are case-insensitive. This is expressed fairly unnoticeably in the spec, but it is there: target = frame-target [CI] with CI being a link to a legend that says: "The value is case-insensitive (i.e., user agents interpret a and A as the same)."