In a web page table, once you have set the width of a cell, that value will apply to the width of all the cells in that column - either above or below. You can have a column span the width of two or more COLUMNS but you can't have a column with a width of 30% above or below a column with a width of 40%. Instead, you'll need to create a separate table which has its own independent column widths:

• Click anywhere in the existing table and from the main toolbar select 'Table', 'Select', 'Table'.
• Select from the main toolbar 'Edit', 'Copy'.
• Click immediately below the existing table.
• Select 'Edit', 'Paste' - a copy of the table will now appear immediately beneath the original.
• If you want to change one or more rows in the middle of the original table you'll need to POSITION the cursor below the copy of the table and select 'Edit', 'Paste' to INSERT ANOTHER copy as you want the original layout to continue afterwards.
• In the table that you want to have a different layout, select the duplicate cells you don't want, right-click and select 'Delete Cells'. 
• In the original table, delete the duplicate ROW or rows that appear in your new table. 
• If you pasted another copy of the original table beneath the new table, you'll also need to delete the duplicate cells.

You can now set the widths of the new table independently of those set in the original table - to set an equal width to each column in a row, select the entire row, right-click and select 'Distribute Columns Evenly' or set the widths of the columns via 'Cell Properties'.

In a web page table, once you have set the width of a cell, that value will apply to the width of all the cells in that column - either above or below. You can have a column span the width of two or more columns but you can't have a column with a width of 30% above or below a column with a width of 40%. Instead, you'll need to create a separate table which has its own independent column widths:

You can now set the widths of the new table independently of those set in the original table - to set an equal width to each column in a row, select the entire row, right-click and select 'Distribute Columns Evenly' or set the widths of the columns via 'Cell Properties'.