How to get rid of ads that won't go away

[licia]

Sometimes there is an ad at the top of the page in the way of whatever I want to search - the ad won't go away and there is no "close". How do I remove it?

 

[babetoo]

couple of times i had to reboot to get rid of them. annoying aren't they. if they do have a x button, they really hide them well.