Limits :
Google has language, domain, date, filetype, and adult content limits. The date limit , added in July 2001, is only available on the Advanced Search page. Only three options are available: Past 3 Months, Past 6 Months, or Past Year.

The file type limit , added along with the addition of other file types to the Google index, was added to the Advanced Search page in Nov. 2001. The Advanced Search page only offers file type limits under the label of File Formats for PDF, Word (.doc), Excel (.xls), PowerPoint (.ppt), and Rich Text Format (.rtf). Using the filetype: prefix, the file type limit can also be used for PostScript (.ps), Text (.txt), .htm, WordPerfect (.wpd), and other file extensions. To use the prefix command, just put the extension immediately after filetype: as in differentials filetype:ps .

Google introduced the language limit in April 2000 with eleven languages which was expanded as of Aug. 2000 to 24. As of July 2001, Russian was added. In Nov. 2001, Arabic and Turkish and then in early 2002 Catalan, Croatian, Indonesian, Serbian, Slovak, and Slovenian joined the group for the following 34 language limit options. These are available on the Advanced Search page and their Language Tools page.

• Arabic
• Bulgarian
• Catalan
• Chinese (Simplified & Traditional)
• Croatian
• Czech
• Danish
• Dutch
• English
• Estonian
• Finnish
• French
• German
• Greek
• Hebrew
• Hungarian
• Icelandic
• Indonesian
• Italian
• Japanese
• Korean
• Latvian
• Lithuanian
• Norwegian
• Polish
• Portuguese
• Romanian
• Russian
• Serbian
• Slovak
• Slovenian
• Spanish
• Swedish
• Turkish

To choose more than one at a time use the preferences page, which also offers a choice for which of 14 languages the surrounding text will be displayed in.

In May 2000, a family filter was added which tries to exclude adult Web pages. Turn it on from the preferences page or in the Advanced Search . By default, "Moderate Filtering" is turned on which is supposed to "Filter explicit images only." In other words, the Web (or text) search is not filtered, but the image results are. The Strict Filtering option which will "filter both explicit text and explicit images" will turn on the filter for the Web and Images databases (and the Directory) but not Groups, News, and Froogle. Some ads will be filtered. Also, the Strict Filtering option will block all results for certain words. However, none of the filters, even the Strict Filtering, blocks all explicit content.

The Advanced Search offers a domain limit , which can be used to limit results to those from the specified domain or it can be used to exclude results from a specified domain.

Stop Words :
Google does ignore frequent words. Its documentation mentions terms such as 'the', 'of', 'and', and 'or'. However, it also notes that these can be searched by putting + in front of them. As of March 2000, 'the' was a stop word that could not be searched even with the + sign. But by 2002, 'the' could be searched with the plus. Be sure to only place the + in front of stop words. If a + is placed in front of a non-stop word in the same query, all + signs will be ignored. As of Nov. 2001, stop words within a phrase no longer require a + sign and will automatically be searched. Also, if only stop words are entered even without phrase markings, they will be searched.

Sorting :
Results are sorted by relevance which is determined by Google's PageRank analysis, determined by links from other pages with a greater weight given to authoritative sites. Pages are also clustered by site. Only two pages per site will be displayed, with the second indented. Others are available via the [ More results from . . . ] link. If the search finds less than 1,000 results when clustered with two pages per site and if you page forward to the last page, after the last record the following message will appear:
In order to show you the most relevant results, we have omitted some entries very similar to the 63 already displayed. If you like, you can repeat the search with the omitted results included .

Clicking the "repeat the search" option will bring up more pages, some of which are near or exact duplicates of pages already found while others are pages that were clusted under a site listing. However, clicking on that link will not necessarily retrieve all results that have been clustered under a site. You can also just add &filter=0 to the end of a search results URL. To see all results available on Google, you need to check under each site cluster as well as using the "repeat this search" option.

Display :
The display includes the title, URL, a brief extract showing text near the search terms, the file size, and for many hits, a link to a cached copy of the page. This cached copy is from Google's index and may be older than the version currently available on the Web. The cached copy will display highlighted search terms. If more than one search term is used, each has a different color highlighting. The default output is 10 hits per screen, but the searcher can also choose 20, 30, 50, or 100 hits at a time on the preferences page. In June 1999, numeric relevance scores and "phase match" or "partial phrase match" indicators were removed. In Sept. 1999, the graphic relevancy bar with its link to a link: search was removed. At the same time, a GoogleScout link was added. GoogleScout is now just labeled as "Similar pages" and find other pages similar in linkage patterns to the displayed hit. In April 2000, Google started clustering results by site. Formerly, hits from the same site would be listed indented under the first. As of April 2000, only the first two hits are displayed (with the second one indented) and the rest available under a
[ More results from hostname ]
link.

With the addition of non-HTML files in 2001, Google added two notes to the display to identify those files. Before the title in the first line of the display, [PDF] or [PS] or [XLS] is used to denote the different file format. On some, a second line of the display lists
File Format: PDF/Adobe Acrobat - View as Text .

Around Aug. 2001, Google started refreshing the indexing of certain pages (those with daily updates) more frequently than the rest of the database. These were marked with "Fresh!" after the URL and size. In Dec. 2001, this tag was changed to list the indexing date. As of Feb. 2002, 3 million pages were being refreshed on an almost daily basis.

Special Search Features :
Cached Pages: Google was the first general search engine that provides access to pages at the time they were indexed, designated as "cached" pages.

Character Searching: Google is also the only search engine that searches for some characters. As of Sept. 2003, it would search for the ampersand & and the underscore _ characters by themselves or as part of a character string. In other words, a search on adv_search gets different results than "adv search" and &tc differs from tc . While it would not search # or + in most cases, it does differentiate c# , c++ , c+ , and c . It does not, however, differentiate c* , c+@ , or c+- , interpreting c* as c and both c+- and c+@ as c+ . (These c+ type strings are all various programming languages.) In March 2004, it started searching for the $   when it precedes a number (see more details on number searching below). Other punctuation marks may change the sorting of results. Tomi Häsä reports that searching for I/O works as does searching for sharped musical pitches as in a#, c#, f#, and g#. The &, + and _ also can be used one or more times in the middle or at the end of a character or a word or between characters and words as in a+, a_, C++, page_count, a&b&c, and i&&.

Number Searching: ( New, March 2004 ) Google handles numbers in some special ways and can search for a range of numbers. When it searches for numbers, it also finds numbers with and without commas. The number range search finds decimal numbers within the range as well. In other words, a search like chennai 565011 finds pages with 565,011 while the number range of  5..11 will match numbers such as 5, 7, 9, 11, and 7.23. Both plain number searches and number range searches can be combined with other terms and can be included in phrase searching. 

Number Range Searching Syntax:

• Smaller number, two periods, larger number, as in 5..11 or 987.6..1001.34
• Use the prefix of numrange, a colon, and then the smaller number, a dash, larger number. numrange:5-11 or numrange:987.6-1001.34
• For open ended ranges, just leave off one of the numbers. For example, to search for all numbers equal to or larger than 534, use either 534.. or numrange:534- . To find only numbers smaller than 16, use either ..16 or numrange:-16 (and 0..16 or numrange:0-16 also works).
• A variant of the number search is the price range search. Currently, it recognize the dollar ($) sign when it is placed immediately in front of the number with no space, but it does not yet recognize the pound (£), Yen (¥), or Euro (€) characters yet. Either use the $ sign with the .. syntax as in $5..11 (the second number could also have the $ sign, but it is not required while the first number must have it to work), or use pricerange:5-11 without the $ sign.

Number Searching Syntax Notes:

• Be sure to put the smaller number first or the range operation won't work
• Must be positive numbers (although you may find negatives, the - sign is not searched and is interpreted as a NOT operator)
• Numbers and number ranges can be used within a phrase search
• A plain number search also will match a number with a comma. In other words, 2001 finds pages with 2001 but not pages with 2,001 while 2001..2001
• A number range search, like most other Google searches, will also find pages that do not contain the number but are linked from other pages that contain the number in the linking anchor text. Check the cached copy of the page for a header saying " These terms only appear in links pointing to this page ."

Documentation
Google Help Pages
Google Zeitgeist (search patterns and trends)
Press Releases

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