13. A computing system comprising: a processor; and computer storage memory having computer-executable instructions stored thereon which, when executed by the processor, configure the computing system to facilitate presentation of search result items having varied prominence, the processor being operable, when executing the instructions, to: reference a set of search result items for display within a search results page that are relevant to a search query, the set including web results and instant answers; rank the search result items based on relevance to the search query; determine that a first search result item is to be increased from a first size allocation to a second size allocation that is greater than the first size allocation based on one or more result attributes associated with the search result items indicating that a click-through rate for the first search result item is greater than a click-through rate for at least the second search result item, each of the first search result item and the second search result item being a different set of components displayed as a group adjacent to one another on the search results page; increase a number of components of the first search result item; determine that a second search result item is to be modified to accommodate for the increase of the first search result item to the second size allocation such that the search result items may be displayed in accordance with one or more search result constraints; and present the first search result item having the second size allocation and the second search result item having the first size allocation within the search results page in accordance with the corresponding ranking.
13. A computing system comprising: a processor; and computer storage memory having computer-executable instructions stored thereon which, when executed by the processor, configure the computing system to facilitate presentation of search result items having varied prominence, the processor being operable, when executing the instructions, to: reference a set of search result items for display within a search results page that are relevant to a search query, the set including web results and instant answers; rank the search result items based on relevance to the search query; determine that a first search result item is to be increased from a first size allocation to a second size allocation that is greater than the first size allocation based on one or more result attributes associated with the search result items indicating that a click-through rate for the first search result item is greater than a click-through rate for at least the second search result item, each of the first search result item and the second search result item being a different set of components displayed as a group adjacent to one another on the search results page; increase a number of components of the first search result item; determine that a second search result item is to be modified to accommodate for the increase of the first search result item to the second size allocation such that the search result items may be displayed in accordance with one or more search result constraints; and present the first search result item having the second size allocation and the second search result item having the first size allocation within the search results page in accordance with the corresponding ranking. 15. The system of claim 13 , wherein the second size allocation is selected from among a plurality of predetermined size allocations.