Outdated (Deprecated) HTML in 4.0
APPLET - Tag enabled the running of a Java applet
BASEFONT - Base font change
CENTER - Centered block
DIR- Describes a directory list
FONT - Font change
ISINDEX - Allowed a form to contain a simple string search
MENU - Described single-column menu lists
S - Strike-through text
STRIKE - Strike-through text
U - Underlined text
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This can avoid page errors with browsers that do NOT support things dealing with these operations. While these operations MAY continue to be supported (as opposed to OBSOLETE operations), there is a different, preferred method of accomplishing the same thing in HTML4; in these cases, it is done through CSS.