Filetypes
.html
This type of file is used on millions of servers across the planet. HTML stands for Hypertext Markup Language, HTML uses tags to create a web page. These tags make up a mark up language. The markup language was created by W3C, which is the standard for every web page today, however some people don't follow it e.g. Microsoft. Tags are used to structure the page and can also describe the appearance of the web page. In 2000, HTML was replaced with a new language called XHTML which followed stricter rules. HTML came in different versions but the mostly common one used is 4.01. When HTML is used on its own (No Scripts), it becomes very efficent (performance wise), because the pages are only a couple of kilobytes (3 - 5 kb) and with todays broadband connections, pages can load up instantly. Browsers (software) have improved very much since a decade ago, which allows these browsers to handle data much more faster and in a more effective way. HTML with many scripts running, can decrease the download/performance of the webpage. This technology is suitable for anybody, who wants to create webpages or a website.
.html [XHTML Language]
XHTML is successor of the previous markup language (HTML). XHTML stands for extensible markup language, which was made to make a stricter version of HTML but with a new name. The best thing about XHTML, is that you can use your own tags to create up your own markup language. This helps web developers easily find the bit of their web page they want. Normal HTML can be used but in a stricter way, When i say stricter i mean that all tags must have a closing tag because HTML tags didn't always have a closing tag which caused problems for web developers and also it didn't look as 'good'. XHTML was created in 2000 and is being used on servers across the world. XHTML has roughly the same performance as HTML, because it's practicaly HTML with some new rules added to the language (Tags).
.js
The .js file ext0ension means a Javascript file. Javascript is a client side scripting language and can be imported into web pages. Javascript can make web pages look and work in more of a dynamic way, This makes a interactive web page for your visitors. Javascript can be imported into page with the <script></script> tags and can be linked if you don't want your script in the page (src="myscript.js"). Javascript was created Netscape Communications, which was imported into their browser (Netscape). Other browsers started putting this language into their browser so everyone could read java scripted pages. There are many versions of javascript which have been created. JavaScript scripts are usually very small files (3 - 8 kb), which usually don't impact performance, unless there are many. This technology is suitable for anybody, who wants to have active content on their webpages.
.vbs
The .vbs extension means a Visual Basic Scripting file or VBScript. VBScript is a active scripting language created by Microsoft. It is a limited version of the language Visual Basic. VBScript is related to javascript because they both can be imported into web pages. VBScript would only work in Microsoft Internet Explorer so other browsers couldn't view the active content of VBScript in web pages. VBScript files were also misused, so they could create email worms which can infect many computers and could be run from the users computer as a file (Windows Script Host). VBScript files are not mainly used today because the language is out dated and many browsers don't support it because of its security issues. VBScript files are usually small files (3 - 8kb), but because the technology is no longer supported by Microsoft. If the VBScript contains code which performs big operations e.g. move files, It could cause a slow down in performance on the computer, but if this technology is used for web, it should be fine. I don't recommend this technology to anyone.
.css
The .css extension means Cascading Style Sheet file. Cascading style sheets (Css) are imported into web pages and can be used with HTML tags. Css is the way to style your pages with colour, style etc.. in a effective way. HTML is only used for layout but not style. Css is effective way of styling your web pages because you could change the style of 500 pages without having to go into every page and change the properties on tags. Css was created by W3C (World Wide Web Consortium) and it's used on millions of web pages across the world. W3C created Css in 1994. Css files are usually small files (3 - 4 kb) and don't decrease performance, unless there are many (unlikely). I would choose this technology to design webpages, because of functions and its performance.
.jpg/.jpeg
The term JPEG stands for Joint Photographic Experts Group. The company came together in 1986 to create a standard which would change the way we use images today. They basically created a image format that could include more than 256 colours and the file size would be generally smaller than the other image formats e.g. BMP, GIF. The company issued the ISO standard in 1992 and was approved by 1994. The JPEG format is used across the world today and is also free for people to use and share. Most modern operating systems include this standard and is preferred to other formats e.g. GIF, PNG. JPEG formats use a certain amount of colours which is the weakness in this format. This is where other formats fill in the gaps for jpeg, so different formats are used for different purposes. Jpeg files can usually be 0 - 5mb in size (Depending on quality and size). This file type should only be used for photographs or small sized images, and shouldn't be placed on a server unless It doesn't consume alot of space. This is because people with slower connections will suffer with a long download, and it will consume much of the bandwidth, which will produce higher costs.
.gif
The .gif extension means Graphics Interchange Format. GIF is a 8 bit bitmap image format that was created in 1987 by CompuServe. The GIF format supports up to 256 colours so the file size is usually small. The format is not suited for photographs because of its limited colour range which would bring down the quality of the picture, however GIF's are good for animations and small images which don't require many colours. The point of the format was to replace the old black and white one which was RLE. GIF files can usually be 0 - 2mb in size (Depending on quality and size). The GIF format is a good choice for people with slower connections and will reduce the cost of hosting, because less will be downloaded and will cause visitors to be pleased.
.bmp
The .bmp extension stands for Bitmap file format. This format is used to store high quality colours photos and other types of pictures. In a web site, I personally wouldn't use this format because all the colours used to make it look high quality can make the file size very large, which is bad for people with slower connections, as I will explain in performance issues. This format is unofficial, meaning it won't work on all operating systems. This format only works on Microsoft Windows and OS/2 and was also created by Microsoft. Files produced in this format shouldn't be placed on web servers, because they consume high amounts of space and bandwidth. The default size of a file in this format is usually 3 - 5 mb.
.pl
The .pl extension is used for the Perl programming language. The perl language was created in 1987 by Larry Wall and is also used on many workstations/servers around the globe. Perl is mostly used on the unix/linux operating system and has been made to work on Windows with ActiverPerl. The programming language allows you to do what many other programming languages do e.g. network programming, GUI's, Web development. On web servers, perl is mostly used for shell scripting and handling with files and databases. There have been 5 versions of perl but the most up to date version is 5.5. Perl scripts don't have much impact on performance, but it depends on the functions used in the script. Perl scripts can usually be 0 - 5 KB in size and should only be used if scripting is required on the server e.g. automated tasks.
.java
The .java extension is used for Java programming language. These java files are compiled into applets which can be imported into web pages to provide dynamic content and programs. The applets are compiled with the java compiler (SDK Kit) and are embedded into the html with the <object></object> tags. The Java programming language was created in 1995 by James Gosling. The programming language only succeeded because it could be imported into web pages and also improved the C language however, it is based on the C syntax. Java can be used to make programs as well (.jar). Java files usually can be 0 - 50 KB in size and don't consume high amounts of space or bandwidth. If you have a programmer's website, posting code shouldn't have any effect on bandwidth (Unless theres lots).
.swf
The .swf extension is a proprietary vector graphics file format. The swf stands for Shockwave Flash, It was created by Macromedia but Adobe brought the company. The format can create animations and animated graphics to create dynamic content for web pages e.g. movies, games, menus. The format is widely spreaded across the globe because its effective and the file size is usually small however, most browsers and operating systems support this format. This format can be created in a piece of software called Adobe Flash. SWF files are usually 0 - 12mb in size and can consume high amounts of bandwidth and performance. SWF files should only really be used if your website provides flash games/movies, and has a good hosting package that you can afford.
.svg
The .svg extension stands for Scalable Vector Graphics. The svg format can be represented in two ways (XHTML, Vector graphics), The XHTML format basically gives a description of the image in tags but the vector graphics format shows a fine degree image in a 2 dimensional view. The advantage of using svg image format is when you increase or decrease the size of the image, it doesn't lose quality. The bitmap image formats (.jpg,.gif,.png) lose quality when they are increased or decreased in size. The svg format was created by World Wide Web Consortium's SVG Working Group. svg files are usually 0 - 2MB in size which won't consume much performance or bandwidth, which is good. svg files should only be used if you are required to resize your images from time to time, or you wish to save bandwidth.
.php
The .php extension stands for PHP Hypertext Preprocessor. It is classed as a programming language to make web pages more dynamic. This scripts are executed on the server, so the client doesn't see what goes on inside your web page. The language can be used in a console view or a graphical interface (programs) and has the ability to connect to MYSQL databases to retrieve or change data in the database, which can be effective and efficient for forums/banks etc.. PHP was created in 1995 by the PHP group. PHP files are mostly small in size (0 - 4 kb) (Less bandwidth), but can consume vast amounts of performance (Depending on functions). Only use PHP, if you want to create interactive webpages or you want to interact with MYSQL databses (Add users etc..), that your hoster provides.