1. Background images aren't clickable
2. The box headings should be content, but they are "invisible" to non-graphical browsers because you've put them only as background images
3. The layout is broken, and the text is overlapping the headings.
A better plan would be to make the headings and the "learn more..." into actual marked-up text, which will allow them to be read and clicked on.
Any posts I write in Arial are on my mobile phone, so please excuse typos etc. Any posts I write in Verdana are on a PC, so feel free to berate me mercilessly for any mistakes