How do I stop a field from auto-adjusting in Firefox (This doesn't happen in Explorer)?

See the picture highlighted in red below where I enter a name and it adds the scroll arrows as if you can add MORE names---when I have specified that only ONE name can go in that field at a time.

My 2nd question is how can I change the site that users are directed to if they select CANCEL---(highlighted below in yellow)----right now it directs them to a list that I don't want users to see.