Solution : https://service.sap.com/sap/support/notes/561792 (SAP Service marketplace login required)
Key words : 
dialog box 'tools' -> 'internet options', symptom bw web applications place, 'icm/http/server_cache_0/expiration', 'temporary internet files' field, bw web applications, stored pages' field, check box 'delete, web application server, max-age reason, valid time stamp
Related Notes : 
       
| 681804 | Configuration of MS Internet Explorer 5.5 and 6.0 for BW | 
| 556854 | Compressed transfer and Browser caching of MIME files | 
| 550669 | Compressed transfer of BW Web Applications | 
| 529241 | Invalidating the cache of the Web Applicaton Server |