The border is caused by the fieldset in each template page in your theme. You can change them like this: use an inline style in your theme templates like this:
<fieldset style="border: 0px;"> template content fieldset>
Or you could add this to style.css
fieldset.custom {
border: 0px solid #fff;
}
Then in your templates change them to this:
<fieldset class="custom"> template content fieldset>
you could also use the above to customize your fieldset so it is diff from default. as a rule, try not to use inline styling. In order to see the changes, Don't forget to set your templates to update in sytem admin. You may also have to delete files in templates_c folder AND your browser's cache.
Addition
As noted in the forum post related to this,if you add the following to your style.css etc
Quote:
It will remove the line. Specifying a line thickness and color will change the color accordingly.