How to make one cell on a table larger?

for the first part of your question i should say tables don't work like that you can't just make one cell larger than the others if you change one cell the whole column would change to achieving that you can make a larger <td> for your last cell and then align the upper cells to left , or you can use colspan attribute to span a single cell.

and for the second question you can apply this method which is looking for each corner cell and applying the radius for that corner to each of those cells, like so:

table > :first-child > tr:first-of-type > :first-child { border-radius: 5px 0 0 0 }
table > :first-child > tr:first-of-type > :last-child { border-radius: 0 5px 0 0 }
table > :last-child > tr:last-of-type > :first-child { border-radius: 0 0 0 5px }
table > :last-child > tr:last-of-type > :last-child { border-radius: 0 0 5px 0 }

Now, this works all fine and dandy for your average table which is a perfect grid of rows and columns with no random row-spans or column-spans,but if you have them you can try using attribute selectors. Maybe something like this:

table > :last-child > tr:last-of-type > :only-child { border-radius: 0 0 0 5px }
table > :first-child > tr:first-of-type > :last-child[rowspan="2"]{border-radius: 0 5px 5px 0}

I make a simple pen for you in Codepen to see what i mean and play around with it

http://cdpn.io/tGbcs

thanks, using a form now!