If you want to build a header or banner from scratch and enjoy being creative then take a look at :
www.bannerfans.com - IT'S FREE!!!!

It's really easy to use:
For this Example I'm going to use the Twenty Eleven Theme from Word Press (a free theme) and have decided to create my own banner.
You will need to determine the Header dimensions , as the header will need to sit properly in the head section.
To do this - point your mouse over the twenty eleven header and right click.
Select View Image Info and from there you will see Dimensions of 1,000px × 288px

Now go to the website www.bannerfans.com

Layout - select your layout
Select your banner size: Select Custom and change Dimensions 1000 px wide and 288 px high
Select a background mode: In this case I will select use gradient color fill.
This prompts you to select 2 colors for a fade in fad out effect
Choose your gradient colors: select your 2 colors to do this by clicking on the box and a color chart will pop up - move your mouse around to select your colors.
Select gradient mode: I have gone for the Horizontal Mode for the fade effect.
Now update your Banner to see how things look

Text and Fonts : lets select some text to go into the your Header ie your Website Name and slogan.
Line 1 : type in your website name
Line 2 : type in your slogan or info about your website
Font Face: the text syle of your font
Font Size: Select a size that stands out (For line 1 - your website name) - I would go for 40px and above in the example I used 50px. for Line 2 your slogan Is used a smaller size of 32px.
Color: Text Color
Rotation: angle of text alignment
Lets update Banner and see how it looks.
You'll notice that the text is sitting on top of each other

Click on Reset lines and click and drag your text so that the alignment sits where you want it to sit in your header.

Shadow and Effects:
This will give you a shadow effect for your text
Shadow position: position of shadow text
Distance: depth of shadow text
The rest of the options are easily operatible and I leave you to try them out.

Border: select a boder if desired
Format : you will need to save this file either as a png or jpeg or gif
Update the Banner and Download directly to your computer.I have not stated the sequence of how to download as everbodys operating system may be different.
Just make sure that it saves or copy it from the software program that the banner dowloads to.

You can select save from the website bannerfans.com but this will promt you to register with the website which might be a bit long winded.