One possible cause could be that the text size are set different on each browser. The smaller the text, the more you'll see and the larger it gets, the more disappears. If only frames would adjust accordingly.
The best thing i can suggest if that is the problem is that you make an image with your 3 lines of text. Place that in the frame as the height of the image is fixed. That shud solve it.
Another suggestion, get rid of the frameset and add the text to each page in a table instead.
I used to like frames but i find that it can cause problems sometimes.
And if the problem is not the text size then errm i just wasted 2 minutes... well it mite help someone in the future so it's all good.. hapy designin :D