Pages should be tested with as many browsers as possible, particularly if you are using HTML extensions specific to a particular browser such as Netscape or Microsoft Internet Explorer. Browsers which don't understand particular tags are supposed to ignore them. However, they occasionally behave unpredictably. Also, some browsers are more lenient than others about HTML syntax which is not strictly compliant to standards.

Elements to be particularly careful of when testing include image maps, tables, frames, and JavaScript. One caveat: sometimes even the same browser will behave differently on different platforms. For example, a particular feature may work fine on the PC version of a browser, but not on the Unix implementation. This is because often separate development teams work on each platform, releasing their own versions incorporating new features at different times and, potentially, with different bugs.


It is important to keep in mind that not all World Wide Web browsers support graphics. Some, such as lynx, can run on terminals such as the VT100, and offer the advantage of much faster performance in low network bandwidth conditions. Therefore, it is necessary to assign a word or phrase to replace each image when it cannot be displayed. This can be done using the ALT modifier tag. If you do not want anything to appear in place of the image, then define the tag to be ALT="". Otherwise, the default tag "[Image]" will be assigned. These tags have been defined for the images linked to this document. See the source html page for an example. ALT tags are now required for ALL images to conform to section 508, a Federal law. Read more about ALT tags.

Style Guide Readability
Device Independence
HEASARC Specifics

Page author: Karen Smale

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Last modified: Monday, 19-Jun-2006 11:24:57 EDT