It can depend on where you are entering the HTML.
Some people can use different HTML in comments than in stories for example. Here is the HTML you are allowed to use.
Comments
Allowed HTML:
<SMALL></SMALL> <STRIKE></STRIKE> <A [HREF] [NAME]></A> <DT> <TT></TT> <CENTER></CENTER> <OL [VALUE] [TYPE] [START]></OL> <SUP></SUP> <CITE></CITE> <CODE></CODE> <I></I> <UL [TYPE]></UL> <BR> <BLOCKQUOTE [TYPE]></BLOCKQUOTE> <STRONG></STRONG> <DD> <WBR> <EM></EM> <ECODE></ECODE> <P> <HR> <SUB></SUB> <BIG></BIG> <B></B> <LI [VALUE]> <DL></DL>
Story Intro text
Allowed HTML:
<SMALL></SMALL> <STRIKE></STRIKE> <A [HREF] [NAME]></A> <DT> <TT></TT> <CENTER></CENTER> <OL [VALUE] [TYPE] [START]></OL> <SUP></SUP> <CITE></CITE> <CODE></CODE> <I></I> <UL [TYPE]></UL> <BR> <BLOCKQUOTE [TYPE]></BLOCKQUOTE> <STRONG></STRONG> <DD> <WBR> <EM></EM> <ECODE></ECODE> <P> <HR> <SUB></SUB> <BIG></BIG> <B></B> <LI [VALUE]> <DL></DL>
Story Body text
Allowed HTML:
<SMALL></SMALL> <STRIKE></STRIKE> <A [HREF] [NAME]></A> <DT> <TT></TT> <CENTER></CENTER> <OL [VALUE] [TYPE] [START]></OL> <SUP></SUP> <CITE></CITE> <CODE></CODE> <I></I> <UL [TYPE]></UL> <BR> <BLOCKQUOTE [TYPE]></BLOCKQUOTE> <STRONG></STRONG> <DD> <WBR> <EM></EM> <ECODE></ECODE> <P> <HR> <SUB></SUB> <BIG></BIG> <B></B> <LI [VALUE]> <DL></DL>
Your user bio & signature
Allowed HTML:
<SMALL></SMALL> <STRIKE></STRIKE> <A [HREF] [NAME]></A> <DT> <TT></TT> <CENTER></CENTER> <OL [VALUE] [TYPE] [START]></OL> <SUP></SUP> <CITE></CITE> <CODE></CODE> <I></I> <UL [TYPE]></UL> <BR> <BLOCKQUOTE [TYPE]></BLOCKQUOTE> <STRONG></STRONG> <DD> <WBR> <EM></EM> <ECODE></ECODE> <P> <HR> <SUB></SUB> <BIG></BIG> <B></B> <LI [VALUE]> <DL></DL>
