Is it possible to insert a tab character in HTML instead of having to type
four times?
It depends on which character set you want to use.
There's no tab entity defined in ISO-8859-1 HTML - but there are a couple of whitespace characters other than
such as  
,  
,and  
.
In ASCII, 	
is a tab.
Here is a complete listing of HTML entities and a useful discussion of whitespace on Wikipedia.