colspan is an attribute of the td tag. It allows a table cell to span some columns. See table 1

table 1

cell1	cell2	cell3
cell4 with colspan=2		cell5

You can also use rowspan (see table 1).

table 2

cell1 with rowspan=2	cell2
	cell3
cell4	cell5

Or combine both (see table 3)

table 3

cell1 with rowspan=2 and colspan=2		cell2
		cell3
cell4	cell5	cell6

cellpadding controls the distance between a cell's border and the content. For the first table I set it to 0, for the second to 20.

cellspacing controls the distance between borders. (table 4 uses 0, table 5 uses 20)

table 4

cell1	cell2
cell3 with colspan=2

table 5

cell1	cell2
cell3 with colspan=2

To control column width you can either set width within the td tag or insert a colgroup tag:
<table>
<colgroup>
<col width=200>
<col width=500>
</colgroup>
<tr><td> ...
You can use span in the col tag to get columns of the same width as in
<table>
<colgroup>
<col width=200>
<col span=3 width=500>
</colgroup>
<tr><td> ...
gives you a table with one column of 200pixels and 3 of 500 pixels width.