PNG: This is another graphic related 3 letter acronym. PNG is a bitmapped image format that employs lossless data compression. PNG was created to improve upon and replace GIF (Graphics Interchange Format) as an image-file format not requiring a patent license. It is pronounced "ping" or spelled out as P-N-G. PNG images can either use palette-indexed color or be made up of one or more channels (numerical values directly representing quantities about the pixels).
SITEMAP: This is sometimes confused with a flowchart of a website. A sitemap is a representation of the architecture of a web site. It can be either a document in any form used as a planning tool for web design, or a web page that lists the pages on a web site, typically organized in hierarchical fashion. This helps visitors and search engine bots find pages on the site. Current SEO thinking is that all websites should have a sitemap - let us know if you need one added to your website!
SWF: Not to be confused with single white female - SWF is a type of file. It is currently the dominant format for displaying animated vector graphics on the web (think Flash files). Based on an independent study conducted by Millward Brown, over 99% of web users now have an SWF plugin installed, with around 90% having the latest version of the Flash Player. It is pronounced "swiff".
If this list of terms just isn't enough, check out some of our favorite web dev spots:
alistapart.com
csszengarden.com
google.com
htmlplayground.com
webworkerdaily.com