w3c

This URL conveys information about the application's architecture and database. Developers usually hide the application's infrastructure in the interface (for instance, they choose page titles like "Personal profile page" rather than "QZ7.65"). Revealing vital clues to the internals of the application in the URL contradicts this effort and has serious drawbacks:

• The technical data appearing in the URL creates potential security breaches. In the preceding example, what happens if an ill-disposed user changes the value of the id parameter? Does this mean the application offers a direct interface to the database? Or what if the user tries other script names, like admin.php, just for fun? All in all, raw URLs offer an easy way to hack an application, and managing security is almost impossible with them.
• The unintelligibility of URLs makes them disturbing wherever they appear, and they dilute the impact of the surrounding content. And nowadays, URLs don't appear only in the address bar. They appear when a user hovers the mouse over a link, as well as in search results. When users look for information, you want to give them easily understandable clues regarding what they found, rather than a confusing URL such as the one shown in Figure 9-1.