Imaes are displayed inline by default (no line breaks). If you want to stack some vertically without using <br>s, you would do something like this:
Code:
HTML:
<img src="example.gif" width="100" height="100" alt="a photo of something" />
<img src="example.gif" width="100" height="100" alt="a photo of something" />
<img src="example.gif" width="100" height="100" alt="a photo of something" />
<img src="example.gif" width="100" height="100" alt="a photo of something" />
CSS:
img {
display: block;
padding: 0;
margin: 0;
}
Line-height, spacing, etc. affects inline elements, so once you set the display to block you shouldn't need that anymore. Also, make sure you're using a correct DOCTYPE or IE and Mozilla are going to have plenty of other inconsistencies.
Hope this helps...