Update index.html

index.html

@@ -121,8 +121,9 @@
 	   <ol>
 	   <li>Check the write permissions of your "HGRepo" folder in your web app public path; and set its path in the config file.</li>
 	   <li>Check the write permissions of your "data" folder in your web app private path; and set its path in the config file.</li>
-     <li>Set the default Locale.</li>
-     <li>Set the default Context to PUBLIC or PRIVATE (for a private repository).</li>
+           <li>Set the default Locale.</li>
+           <li>Set the default Context to PUBLIC or PRIVATE (for a private repository).</li>
+           <li>Every picture folder may contain a "thumbs" subfolder - that you should create - to not lack in performance: file names in thumbs must be same of file names in parent folders.</li>
 
 	   </ol>