I am using the following applications: Selenium 2.0 in C# Firefox I need to write a test that clicks a button and opens a frame as a pop up window. The frame does not have a name nor id. The source code in the frame starts with "html" instead of "frame". However, when you right click on the window, it shows that it is a frame. So, I think it is a frame instead of a window. I have tried the following code, but does not work: driver.SwitchTo().Frame(0) The error I get looks like below: error: No response from server for url http://localhost:7055/hub/session/126a4485-48cb-4230-b0b0-69c4169b1852/element/%7B706f4a88-56a7-4813-af1b-8e137ce676af%7D/click Please help. Thanks.