Subject: What Is the Strongest Acid?

My chemistry textbook ("Chemistry" by McMurray and Fay, Prentice Hall, 
1995) ranks strongest acids to weakest in a table on p. 575 as follows:  
HClO4, HCl, H2SO4, then HNO3, and lists HF as a weak acid. However, my 
boyfriend believes HF is the strongest, and found two weblinks stating 
that, one on your own site at 
http://www.madsci.org/posts/archives/aug98/898914315.Ch.r.html, and 
another at http://www.newton.dep.anl.gov/askasci/chem99/chem99182.htm. Is 
my chemistry book in error? Can you point us toward a definitive reference 
source to settle this question? And what is the source of the disparity in 
the sources? Thanks!

Re: What Is the Strongest Acid?