<p>I am currently using a dotted border for certain UI stuff such as instructions, notes, error boxes, etc.</p>

<p>But recently I changed to a solid border, due to a requirement, but I just find it kind of strange.</p>

<p>It seems that by making it solid it puts too much emphasis on page elements which are just informational.</p>

<p>What are your views?</p>

This is a difficult question because it is very subjective.  Many newer websites these days (Stack Overflow included) fore go the border completely and use a more subtle background color difference between the main body color for accented content sections like you mentioned (instructions, notes, etc.).  When I see dotted lines, I intrinsically relate them to abbreviations or acronyms like this:
```
```
<abbr style="border-bottom:1px dotted #000;cursor:help;">
    <span style="cursor:help;" title="Cascading Style Sheets">CSS</span>
</abbr>
```
```
Therefore I would recommend staying away from dotted borders.