URL rewriting is a solution for search engine unfriendly URLs known as "dirty URL". Before you pay for a content management site (CMS) which uses dynamic web pages, ask about URL rewriting from your web developer. Simple, small sites don't even need CMS but if your website for example markets thousands of apartments Australia wide, it's no use displaying to search engines non-keyword rich, unfriendly URLs such as:
www.rumplestiltskin.com/index.php?id=37&PHPSESSID=17e8892d70a7f2e34446c23ba4031304 for a page about electric drill sales in Sydney. This is a "dirty URL"
Good description from Wikipedia:
A "rewrite engine" is software located in a Web application framework running on a Web server that modifies a web URL's appearance. This modification is called URL rewriting. Rewritten URLs (sometimes known as short, fancy URLs, search engine friendly - SEFURLs, or slugs) are used to provide shorter and more relevant-looking links to web pages. The technique adds a layer of abstraction between the files used to generate a web page and the URL that is presented to the outside world.
Search Engine Friendly URLs Rewritten:
Remove query strings. for example:
Rewrite URLs Shorter
Use Lower Case Characters in URLS. Not all web servers treat upper and low case URLs the same.
Set-up your "A" records so that both for example www.4webmarketing.biz and http://4webmarketing.biz work
Guessed URL Map similar URLs for example:
www.domainname.com/apartmentrent and www.domainname.com/furnishedapartmentrent might point to the same web page.
URL typos: Look at the keys of the QWERTY keyboard and imagine a very fast, fat fingered typist with an accuracy of 70% If your domain is worth millions like google.com then if it's not already snapped up by cyber squatters pick up typo crumbs before your competitors do. For US$40 we can send you a typo report. For example the word accommodation is miss typed as often as it is typed correctly:
Tips on How to Set-up Search Engine Friendly DataBases
In summary if planning a dynamic website ask your web developer for URL rewriting. URL rewriting is an extra cost but the best site is useless if it is lost in cyberspace.