to increase web application performance caching is used,
caching may be categorised-output cahce,partial page or 
data cahing.
<@outputcache duration="60" (in min) varyby param=q1;q1)
<@outputcache duration="60" (in min) varyby 
control=dropdownlist1)

partial page -when a portion of page is to be keep track in 
server memory for reusability frequently

data cahcing-
cache["dscache"]=ds  //storing dataset inot cache
dataset objds=new dataset();
objds=(dataset)cache["dscache"] //to get into object dataset