CSS why doesn't this work?

its not showing the right border

<开发者_C百科;th style="border-style:solid; border-right:1px; border-left:0px; border-bottom:0px; border-top:0px;">s
  </th>

Just try

<th style="border-right:solid 1px gray"></th>

You should give border-color as well.

in you css

th.giveaclassname {border:0 1px 0 0 solid black;}

in your html

<th class="giveaclassname">..</th>

or it might be that the borders are collapsing, and the thicker one prevails (see this post)