Opening New Browser Windows

Like most "annoying Web tricks" (such as frames and auto-refreshing pages), there are a few occasions where there's a reasonable use for opening up additional browser windows, such as in letting users bring up reference information to help them in filling out an online form (without the browser leaving the form and possibly losing the data the user has partially entered). For those occasions, here's how to do a new-window link. First, a simple targetted link that opens a new browser window (usually sized the same as the current one):

A HREF="link.html" TARGET="_blank"

Note that the proper target is _blank, in all lower case. There are many mistaken impressions among Web authors of what the correct target is, aided and abetted by the fact that the popular browsers do in fact open up a new window when given any unrecognized target name, but the proper target according to the formal HTML specs is _blank (with an underscore as its first character).

More...
http://webtips.dan.info/new-window.html