Making a html element fixed position relative to background image

I have been using the upfront theme developed by you guys and I am very satisfied with the theme. However, I want to know if it is possible to keep an html element fixed at its position relative to the background. I noticed that when viewing my website from a computer with different resolution, my texts over the background image changes their positions.
FYI my background image is set to full screen and I have attached two screenshots. The first is what I see on my screen and the positions of the texts are where I want them to be. The second screenshot is on another resolution and the texts are elsewhere.

Thank you for your help.