Whether you choose to acknowledge it or not, every Geocaching.com page is really in and of itself a code. You see, all these web pages are written in HyperText Markup Language (HTML). HTML is the standard markup language used to create web pages all across the Internet
. Web browsers read HTML files stored on the server and translate them into web pages you see.
Without turning this into a web design class, all you really need to know is that source code is just the common language between humans and machines. Its made of a well formed structures that the machine can interpret into ones and zeros, which are ultimately displayed by your browser. In the case of HTML, those structures are defined by "tags", which are contained in angle brackets (<>). Most of the time, these tags serve as bookends to the content between them, but there are some tags which are standalone.
Most web browsers allow you to view the source code of a page by right clicking and selecting an option like "View Source", though the exact method may vary (Google can help in this regard). Which respect to geocaching.com pages, there is a lot of source code on a cache page. The good thing for you, the puzzle solver, is that you only need to pay attention to three spots, as they are the only places the puzzle hider has any control over.
Those three are: (1) the page background, if applicable ; (2) the cache's short description; and (3) the cache's long description. The easiest way to navigate the source is to simply search for the tags that are associated with these areas: 
and 
. Looking in these areas will allow you to see some things that sneaky cache owners know won't render in your web browser, like HTML comments (
), or things that a human eye won't catch, like really small images.
Just a reminder that the cache is not at the posted coordinates. You must use the source to find the real coordinates.
