iMac OSX 10.10.3 Yosemite Mail program stuck

I have an iMac....Yosemite....mail program has been not 'normal' for about a week but was working anyway yesterday Sunday July 5 I opened from the NY Times an article about the Cosmos that has streaming videos and ever since I am unable to delete that NY Times page nor am I able to get my mail or send mail. The cursor does not work now in that mail window. I've tried everything to 'delete' the NY Times page however it won't vanish ! I called for Apple tech support only would have to pay $29 for this 'fix' and was told could find 'the' answer online. I am a senior 74 yrs young, artist....limited income. So need help/SOS ! Thank you! Cynthia