Refinement shape content search

Visual incongruity in search result sets may be reduced at least in part by searching an optimized visually significant subset of a category tree that categorizes a collection of content. The category tree may be optimized at build time at least in part by pruning with respect to visual coherence and by the size of the content collection subset referenced by particular categories. Content collection subset sizes both too large and too small can detract from the visual significance of a particular category. The visually significant subset of the category tree may be further optimized at query time by intersecting the visually significant subset with the query-associated sub-tree(s) and further pruning categories in the visually significant subset that have child categories in the visually significant subset. Searching with respect to the optimized visually significant subset can also improve search efficiency.