CS conferences not indexed by Scopus or Web of Science?
That is correct: most good computer science conferences have not been indexed by the standard journal indexes (maybe this will change someday, but it hadn't last I'd heard).  

A good alternative for evaluating the quality of a conference or to search for decent conferences is to use Google Scholar's "venue metrics" function.  For example, searching for "programming" finds top programming-language conferences, such as ASPLOS, PLDI, POPL, and OOPLSA.  It is interesting to note that in these results, if one ignores the non-field "Mathematical Programming", the first journals don't show up until halfway down the list.

Three caveats:


The search isn't currently very smart; it's very literal in its use of words.  Thus, for example, searching "programming languages" doesn't find ICFP.
Only the top 20 venues for a given query are returned, and you can't look for more.
Some decent but highly-specific venues still don't appear.