Don't try to control visitors to you site.
There is nothing more irritating to a user than a site that appears to be trying to control them, either by forcing them down particular paths, of by disabling features of the browser interface. Here are a couple of examples of what I am talking about:
- Opening new windows, so that the original site is still hovering in the background. If the user wants to come back to your site they can click the back button, and if they want to open a new window they can do it themselves.
- Using scripts to disable the back button, disable right clicking, or subvert some other aspect of the browser interface.
These techniques can decrease accessibility as they go against users expectations about how the web works. I expect to be able to click the back button in my browser to move back to the index page of a site, or leave a site altogether. Undermining such conventions can be particularly confusing for the 'non-visual' user, as they may not know that what they expected to happen, has not happened on this particular site.