The source often give clues. Web apps usually populate the source with some relevant meta data. Other than that, Netcraft was useful to know "what's this site

The source often give clues. Web apps usually populate the source with some relevant meta data. Other than that, Netcraft was useful to know "what's this site running?". That gives you clues of the OS and the possible technologies used. ie. http://searchdns.netcraft.com/?host=techcrunch.com&x=0&y=0 http://searchdns.netcraft.com/?host=techcrunch.com&x=0&#... Also you can try post their forms and dig around that to find out clues.