[Latex] use footnote in the caption

1. \begin{figure}[!ht]  
2.     \centering  
3.     \includegraphics[]{ch1_architechture.png}  
4.     \caption{Architechture du système \protect\footnotemark}  
5. \end{figure}  
6. \footnotetext{http://developer.android.com/guide/basics/what-is-android.html}  
7. 
   
8. By this means, the link of footnote is correct.