The most likely cause is that your text font color is too close to the color of your background image. For example, you won't be able to make out much text if you have a largely black background image and you've selected a black font on your Look and Feel page (http://www.xanga.com/CLAF/default.asp).

To fix this, just go to your Look and Feel page and pick a contrasting font color where it says "Normal Text" under "Appearance of Text & Links". For example, if you have a largely black background image, you might choose white as your font color. This should solve your problem!