I don't mean to be rude, but you really need to brush up on your html. :) For example you put <td> around each of the links, but you didn't include a <table> or <tr> tag which would be needed to make <td> mean anything. (Which I don't really think you would need to put <td> in there in the first place) If you want to put tables in there your code would go something like this:
<html>
<body>
<center><br>
<font color="009900">[ Server GM Shop ]</font><br>
<table>
<tr>
<td><button value="S-80 Weapons" action="bypass -h npc_%objectId%_Link merchant/8240-1.htm" width=203 height=21 back="L2UI_ct1.button_df" fore="L2UI_ct1.button_df"></td>
</tr>
<tr>
<td><button value="All Weapons" action="bypass -h npc_%objectId%_Link merchant/8240-2.htm" width=203 height=21 back="L2UI_ct1.button_df" fore="L2UI_ct1.button_df"></td>
</tr>
And so on down the item list.
</table>
</center>
</body>
</html>
Which if you did that, I would add a center align atribute to the table bracket and only have center tags around the text (for "proper" coding) but it would still be easier to just remove the TDs. :P
Also you open <center> but you don't close it. Yes forgetting to close it wont cause the whole script to mess up (until you reach a part you don't want to be centered), but its proper coding.
Just my two cents as a semi knowledgeable coder. Hope I helped!