Why is part of this centre-justified?

Code:             <tr>                 <td colspan="3" class="sheet-statlabel-big" style="font-size: 1.5em; width: 750px;">Skills</td>             </tr>             </table>     <button type="roll" value="/em attempts a ?{Skill name} check.
[[d100<?{skill rating}]]
Success = 1, Failure = 0" name="skill-roll" ></button> Universal Skill Roll     <div class="sheet-tabbed-panel">         <div class="sheet-row-panel">             <input type="checkbox" name="attr_OCC-Skill-toggle" class="sheet-arrow" />             <h4>D20 'Base' Skillset</h4>             <div class="body">             <table style="width:90%">                 <tr>                     <td style="width:10%"></td>                     <td style="width:25%"><h5>Name</h5></td>                     <td style="width:8%"><h5>Rating</h5></td>                     <td style="width:10%"><h5>+/ Level</h5></td>                     <td><h5>Notes</h5></td>                 </tr>             </table>             <fieldset class="repeating_skillocc">                 <table>                     <tr>                         <td><div class="sheet-ability"><button type="roll" value="@{character_name}'s @{skill_name} check:
/roll d100<@{skill_rating}"></button></div></td>                         <td><div class="sheet-ability"><input class="sheet-input-center-aligned" type="text" style="width:220px" value="" name="attr_skill_name" placeholder="Skill name"/></div></td>                         <td><div class="sheet-ability"><input class="sheet-input-center-aligned" type="number" value="" name="attr_skill_rating" /><b>%</b></div></td>                         <td><div class="sheet-ability"><input class="sheet-input-center-aligned" type="number" style="width:60px" value="+" name="attr_skill_level" /><b>%</b></div></td>                         <td><div class="sheet-ability"><input class="sheet-input-center-aligned" type="text" style="width:300px" value="" name="attr_skill_reference" placeholder="Notes here"/></div></td>                         <td></td>                     </tr>                 </table>             </fieldset>             </div>         </div>     </div>     <br>         </table>     <div class="sheet-tabbed-panel">         <div class="sheet-row-panel">             <input type="checkbox" name="attr_OCC-Skill-toggle" class="sheet-arrow" />             <h4>Elective Skills</h4>             <div class="body">             <table style="width:90%">                 <tr>                     <td style="width:10%"></td>                     <td style="width:25%"><h5>Name</h5></td> Screenshot:  "D20 Base Skillset" should be left-justified, like "Elective Skills" and the Universal Skill Roll should likewise be left-justified. Not sure what's going on.  Thanks! Dan

I'd recommend checking your CSS to make sure there isn't something hinky there. Additionally, code is easier to read in forum posts if you post it with code formatting, which is available from the wand button (the first button in the row at the top of the post edit panel).

Thanks Scott. Gotcha! (unfortunately, I have no idea what to do on the CSS page. I barely know what I'm doing on the HTML page!) I guess I'll have a go at it. 

If you put that bit of code in a fresh editor by itself and it is not centered, then you know you have something from the previous code that is affecting it. 

Yep, what Kraynic said. To be fair, I'm not sure what CSS could be in there that would be affecting those two headers differently since they have pretty much the same selectors (e.g. classes, ids, etc) on them, but it's possible there's some sort of nth-child selector being used or something. Also, I'd really recommend not using tables for your sheet layout, especially when repeating sections are in the mix. Trying to mix the two is just asking for headaches from beating your head against styling and button functions. CSS flexbox, CSS Grid, and CSS Multi-column are much better ways to go. Additionally, they make it simple to create a responsive layout, which is difficult to impossible with a table.

Open developer tools (More Tools\Developer Tools) and make sure the Elements tab is selected. Then  right click "D20 Base Skillset" and select inspect.  In the right hand pane in the development tools click the computed tab and look for text-align.