Minor problem but it's driving nuts.

I can't seem to format my text to stay with the font size I selected. Can't do that for individual message or for all messages. I have it set for HTML. I don't have any kind of stationary selected. On Option and Compose tab, it is listed that I have the selected font and font size but when I composing the letter, it is set at a smaller font. When I change it to a bigger size it shows the bigger size in the window but as soon as I clik on the page to continue typing the window shows the fonst reverting back to the smaller size. Even when I select the text to increase size, it won't. What the heck is going on? I am not even sure when this started but I didn't have this problem before.

Send help before I go crazy. Don't know how many time I went to Options and Compose text to redo over something that doesn't accomplish anything. Now that's crazy!