kentico_jurajo wrote: And what if popup windows are disabled? These are things we cannot influence and it is the clients choice. You will need to implement it in other way - e.g. using custom web part and do the redirection in the server side code.
Did you mean using the ASP.NET Response.Redirect() command in the web part code behind? If so, you can't control whether a URL opens in a new page with Response.Redirect() either.
Just to clarify, I ended up using a hard coded <a href> tag to the URL I wanted with a target attribute set to open a new window as a Javascript solution was too unreliable. As you say, there are too many different user configurations that can prevent it from working, so hard coding was the only solution.