Question: I know target="\_blank" is supposed to make the thing open in a new window, and for some browsers, like FF3, it will actually make it open in a new tab. Is there a way to exercise more control over this behavior as a developer?

Answer: 
According to <https://developer.mozilla.org/En/Window.open>, """
**How do I open a referenced resource of a link in a new tab? or in a specific tab?**

Currently, you can not. Only the user can set his advanced preferences to do that. K-meleon 1.1, a Mozilla-based browser, gives complete control and power to the user regarding how links are opened. Some advanced extensions also give Mozilla and Firefox a lot of power over how referenced resources are loaded. 

In a few years, the target property of the CSS3 hyperlink module may be implemented (if CSS3 Hyperlink module as it is right now is approved). And even if and when this happens, you can expect developers of browsers with tab-browsing to give the user entire veto power and full control over how links can open web pages. How to open a link should always be entirely under the control of the user. 
"""
Currently the final decision on how to open a link is in the hands of the user and their browser.

Also, I wouldn't be too happy if a developer overrode my choice in the way that you are describing. I only ever want one browser window open at a time, and do not want child windows to appear. Other people feel much the opposite. We should try to respect that as developers.