Please explain rowspan and colspan, col and colgroup

Question

Can anyone explain rowspan and colspan, col and colgroup? And are these W3C valid and semantically correct? Under which circu

Answer 1

rowspan and colspan are attributes that allow the designer to 'merge' cells - much like the same command in Excel (for example).

col and colgroup allow the designer to apply css to a vertical column, rather than having to apply css to individual cells in a column. Without these, this task would be much more difficult as html tables are row-based.

All four of these are valid.

For future reference, try http://reference.sitepoint.com/html