Testing web pages means knowing browsers and their engines
There’s been some confusion over which browsers a web site should be tested in—if at all. HTML is an interpreted language, which means various browsers that read it may display the same page differently. Each browser has its unique quirks, but there’s a pattern.
| Browser | Displays alt text |
Shows “missing” icon |
|---|---|---|
| Firefox 3.5 | yes | no |
| IE6, 7 & 8 | yes | yes |
| Opera 10 | yes | yes* |
| Safari 3 | no | yes |
All browsers, such as Internet Explorer, Firefox and Safari, use a “render engine” to read HTML and present what people see on screen. If you look at two browsers based on the same engine, you should see very similar pages. Differences arise between browsers that use different engines.
For example, if a web page is missing an image, Safari (Webkit) and IE7 (Trident) show a “broken image” icon. Firefox and Camino (Gecko) show nothing.
Engine list
So which one uses what? Here are the most popular engines and their major browsers:
Gecko (by Mozilla)
Trident or MSHTML (Microsoft)
Presto (Opera Inc.)
Webkit (Apple, KDE)
When troubleshooting sites, anyone on Mac or Windows can view web pages in IE6, 7 & 8 at Geotek’s netrenderer. It’s slow but accurate. Failing that, it’s best to load several browsers onto both a Mac and a PC—or keep in touch with someone willing to test on each platform.
*Opera 10 displays the word “image” if an image is missing and has no alt text.
**As Microsoft moves closer to web standards, different versions of Internet Explorer display pages differently. In particular, IE6 is notorious for its lack of CSS and transparency support.