For the border, I will use this image of some hex signs. My personal feeling is that an image is more pleasing if it is not just one repeated over and over. The several hex signs add variety and interest. You may do as you wish, of course!

I would recommend that you make your border no more than 100 pixels wide. Remember, it takes up text space on your page.

For the dividing border, choose a color from the image using the dropper tool .   I have chosen the dark red. Click on the color you want with the right mouse button; this will put the color in the background color box that is under your color palette on the right side of the work space.

Now go to the menu bar across the top and choose Image, Add Borders. Enter 10 as the size in the Right option; leave all others at zero.  

Now your image should look like this.  

You may choose to have a wider or narrower border than this.

Now we will add a wide border that will be the background of the text portion of your page.

Use your dropper tool and choose a color for your background; I used the background color of my image (Remember to use the right mouse button). Go to Image, Add Border and use the setting 1100 for the right border this time and click OK.

Wow! see how wide that is? That will give you a nice background no matter how large your page is. Here is what mine looks like.

You could stop right now and it would be a nice bordered background, but....... I think it would be nicer to add a few special effects.

Choose your magic wand tool.  
Click on the dark red divider border; this will select it-you will see a marquee telling you it is a selection.

On your menu bar, choose Image, Effects, Drop Shadow. Use the settings I show below.

They are: Color- Black (it will most likely be there already), Opacity- 80, Blur- 5, Vertical- 1, Horizontal- 1. You can check to see if this is what you like by click/dragging the 4-way arrow under the preview window. Click OK.

This gives you a nice shadow on the right side of your divider border. But wait! we're not done!

Leave the marquee around the divider. Go to Selections, Invert.
Go to Image, Effects, Drop Shadow; again click OK.
Here is the border with shadows on both sides of the divider to set it off.
Right click to remove the selection marquee.

Now I am going to show you how to check the bordered background you just made to see how it looks when it tiles on a page. There are several ways to do this; I will show you the one I use.

Open a new image 400 x 400.
Go to you Flood Fill tool.  
When you open the Tool Options Palette, this is what you will see:  
Choose the Pattern option under the Fill style. Then click on the second tab, the one with the grid pattern.

This opens more options. You may choose what you want to Flood Fill with! Choose the label of the image you have just made. It will appear in the window. This is mine and what I named it: sb1. (for side border 1)

Now click on the new 400 x 400 image you have, to activate it. Now Flood Fill it by clicking on the center of it.
Ta Da!!   you now see your border "tiled"! Only once, but tiled. Here is mine.

This is the center section--you can see the numbers on the side to compare with yours.

The break you see in the divider needs to be eliminated. This is very easy to do.

Go back to your original image.
One of the easiest ways to fix the break is this:
Go to your Selection Tool.  

Use this tool to select an area in the middle of the background divider.

This is a very useful procedure to learn. What this does is put a copy of this section, as a new selection, onto the original image. You will have an image that looks something like this:

You will see that it is "attached" to your cursor, and that you can move it around. Click and drag this section to the top and match it up to the divider bar. It may make it easier to zoom the image and focus on that section.

Now click the Paste As A New Selection again and another copy will appear. Do the same thing to the bottom of your image.
Now you have successfully replaced the "break" with a solid shadow that goes completely to the top and bottom. Now you can use the right click to deselect the section.

Now check it again in your 400 x 400 new image by flood filling as we did before.

Here is the section that had the break. You can see that the background tiles with no break because we fixed the shadow.

Save this bordered background as a gif and you're ready to go! Now you can use this background on a page and it will look terrific! Place it in the Body tag as Background=" your new image .gif" It will automatically tile when it is here. If you forget to put it in the body tag, it will only display one time, as the .gif it is. If this happens, check where you put it in your code.

I hope you have had fun and made a great side-bordered background. Please send me mail and let me know where you use your new creation.