eyesightthe main advantage of such minimal urls is that they don' need to be changed if you ever move your pages to new directory or server--the server and path are inferred when the page is usedthey are not hardcoded into its html the flipside of this can be fairly painfulexamples that do include explicit site names and pathnames in urls embedded within html code cannot be copied to other servers without source code changes scripts and special html tags can help herebut editing source code can be error-prone the downside of minimal urls is that they don' trigger automatic internet connections when followed offline this becomes apparent only when you load pages from local files on your computer for examplewe can generally open html pages without connecting to the internet at all by pointing web browser to page' file that lives on the local machine ( by clicking on its file iconwhen browsing page locally like thisfollowing fully specified url makes the browser automatically connect to the internet to fetch the referenced page or script minimal urlsthoughare opened on the local machine againusuallythe browser simply displays the referenced page or script' source code the net effect is that minimal urls are more portablebut they tend to work better when running all pages live on the internet (or served up by locally running web serverto make them easier to work withthe examples in this book will often omit the server and path components in urls they contain in this bookto derive page or script' true url from minimal urlimagine that the stringappears before the filename given by the url your browser willeven if you don' html file permission constraints one install pointer before we move onif you want to use different server and machineit may be necessary on some platforms to grant web page files and their directories world-readable permission that' because they are loaded by arbitrary people over the web (often by someone named "nobody,who we'll introduce in momentan appropriate chmod command can be used to change permissions on unix-like machines for instancea chmod filename shell command usually sufficesit makes filename readable and executable by everyoneand writable by you only these directory and file permission details are typicalbut they can vary from server to server be sure to find out about the local server' conventions if you upload html files to remote site these are not necessarily magic numbers on unix machinesmode is bit mask the first simply means that you (the file' ownercan readwriteand execute the file ( in binary is --each bit enables an access modethe two (binary say that everyone else (your group and otherscan read and execute (but not writethe file see your system' manpage on the chmod command for more details server-side scripting