Even if you are in an automated context, not using a typical browser, fetching the data/webpage from an URL is easy. There are command line tools like wget and curl, and every programming library has its share of libraries to build on.
But what if you need the HTML …
Note to self: short list of useful options of wget for recursive downloading of dynamic (PHP, ASP, ...) webpages (because wget's man page is too long):
--no-clobber: do not redownload pages that already exist locally.--html-extension: append extension .html to webpages of which the URL does not end on .html or …