COLSPAN allows you to merge cells across columns
ROWSPAN allows you to merge cells across rows
For example, the following code:
<HTML>
<HEAD>
<TITLE>Example of a Table</TITLE>
</HEAD>
<BODY>
<TABLE BORDER>
<TR>
<TH COLSPAN=2></TH>
<TH>Employee<BR>Name</TH>
</TR>
<TR ALIGN=CENTER>
<TH ROWSPAN=2>Employee 1</TH>
<TH>First</TH>
<TD>John</TD>
</TR>
<TR ALIGN=CENTER>
<TH>Last</TH>
<TD>Smith</TD>
</TR>
</TABLE>
</BODY>
</HTML>
Would produce:
Employee
Name
Employee 1
First
John
Last
Smith