Compatibility issues - Each of us can see the same web page in a different manner... |
| If you want to write great web pages, you have to know something: each of us can see the same page in a different manner. Why? Well, because you see the web page in a different manner according to the used hardware, the running operating system, your screen resolution, the used browser, the browser version and finally the browser error tolerance. In other words, your fantastic web page could look as a very bad page displaying it on other machines. If the worst comes to the worst, somebody couldn't see your web page at all! So your problem is: do I want to show my great page to all people of all over the world or simply I'm writing a cool page for few persons? In the first case, well, forget big images, forget cool DHTML, forget CSS1 or CSS2, forget JavaScript, forget ASP, forget frames...What do you get now? Just pure, simple HTML 2.0! Wow! Well, you have to forget clickable images and tables too...If you do that, your page will look great to all visitors! On the contrary you could want to sacrifice your page visibility simply because you want to use a very cool script your grabbed on the net...So you have been warned: if you want to build a cool dynamic navigation bar for example, well, many visitors couldn't see your page... Anyway I have to say that the Internet is a very quickly growing world, and tomorrow who can knows, maybe all visitors will be able to see your page... While I'm writing, there are some good news on the air: I read something about GECKO, the next Netscape's browser. They said that it will support *ALL* W3C standards (CSS1, CSS2, DOM, XML just to say some of them). So what can I say? I think you have to know how things are now, then you will decide by yourself... Operating SystemYou have to know that some web browsers aren't available for all platforms! So if you check out your page using a certain web browser, consider that other visitors running a different operating system could use a different web browser. In addition some special HTML tag working on a specific browser could be not working on other browsers. A little example? The <MARQUEE></MARQUEE> tag it's a proprietary MSIE's tag. It means that you can't see it working if you use a different browser (Netscape Navigator or Opera for example). And, as far as I know, there isn't an Internet Explorer version working on a Linux operating system...did you get me? All Linux users will not be able to see that tag! Another example: you want to use an clickable image as a navigation bar...so all visitors will be able to navigate your site clicking on that image. Great! And what's happen if one visitors of yours disable images? Or if he uses a text browser such as Lynx? Simple: again he won't be able to visit your site! But these are little examples: remember that there are several operating systems around... Screen ResolutionAny image you see on your monitor is an image composed by dots. There are thousands of dots in your screen. These dots are called 'pixels'. You can think of a pixel as a very little light bulb. Each of these 'light bulbs' can be switched on or off. Besides each of them can be colored. To see pixels, observe your screen using a magnifying glass: you will be able to see these 'light bulbs'. The amount of pixels is called 'screen resolution'. The more 'light bulbs' your screen have, the more definite images are. The resolution that you have depends on your video board and your monitor and it can be considered as the geometrical screen area. Your screen can be represented as a rectangle so its resolution is determined multiplying its width by its height (to know a rectangle's area you have to multiply its width by its height). Well, there are several screen resolutions, but the commonest is 800x600 pixels. Anyway there are other screen resolutions (640x480, 1024x760 or 1280x1024 for example). Ok, where is the problem? The problem is scrolling. If you design an image considering a certain screen resolution, you could have problems with lower screen resolution. For example, suppose you are using a 1280x1024 screen resolution and you build a great image as large as your screen: what's happen when you see that image using a lower screen resolution? Well your page will be too wide to fit within the screen resolution being used, so your browser automatically will insert scroll bars into the page. For this reason you should design your pages to fit the lowest resolution. Anyway, as I said the most used screen resolution is 800x600. Used BrowserAccording to the used browser result maybe unpredictable! A little example? Too much often I see whole sites using ONLY graphics inside. They forget simple text. I mean that you have to click on their absurd image maps to navigate the site and you have not other chances. Great! And what happens if I decide to disable images on my browser? Remember there are some TEXTUAL browsers that can't display images at all! For example the great Lynx. So they forget to add textual links too. In addition, browsers are not equal. So if something is working on a certain browser maybe it couldn't work on a different browser. Another example? Use ActiveX and try to make it working with a browser which isn't MSIE. It's impossible, because ActiveX is a proprietary product. It isn't a standard. But JavaScript it isn't a standard too! And these are just some examples. The solution? Use standard HTML only. Try your pages with different browsers. I suggest you these browsers: MSIE (MicroSoft Internet Explorer) Netscape Navigator (or Communicator) and Lynx. You could discover interesting things (for example did you know some browsers don't support tables? Build a table and try to see it using Lynx...). Browser VersionAccording to the browser version result maybe unpredictable! Just a little example: sometimes people write to me asking for a DHTML course (Dynamic HTML). Well, you have to know that visitors using browser versions less than 4.0 can't see DHTML based pages. There are a lot of people still using versions 3 or 2. They can't see DHTML pages. Another example? Frames. Older browsers can't see frames. Again, use HTML 2.0 and you will avoid these problems. Errors ToleranceThis was a great surprise to me too...you have to know that browsers aren't equal. Some of them are too much tolerant with errors. Again a little but really explanatory example: <html><head><title>Tolerant browsers</title></head> And now check it with: Netscape Communicator (tolerant), MSIE (tolerant), Mosaic (intolerant). You will notice that MOSAIC will not show the last line, because when it parse the HTML page it notices the '<!--' tag and it knows that anything it encounter until the next '-->' is a comment...So it won't display anything until the next '-->' group of symbols. Remember: any comments starts with '<!--' and ends with '-->'! So too much tolerant browsers are not useful, because many web authors are unaware of their errors, simply because they check their pages with too much tolerant browsers... SuggestionsOk, now let's see some suggestions to build good web pages:
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