Centering within a div CSS/HTML

[Django x2]

I want to center a SharePoint search box. In SP Designer, if you add a tab prior to the box, it adds a <div style> box. Putting margin-left:auto;margin-right:auto; here doesn't center the object.

Given that this is within SharePoint, I can't just hack about with the css and add ids where I like. I guess I can inline CSS, but nothing I've tried seems to work.

Any ideas?

 

[Django x2]

which we can't do really as that would mean defining a screen size. i.e. 800px on a 1400x900 screen is different to a 1024x768 res, etc.

Div align is not valid in SharePoint either as it does not meet the strict transitional type