Anyone can draw up a design in Photoshop. That doesn't make them a web designer. I have worked with artists and graphic designers that can create some pretty cool looking "layouts" but the problem is they can't be converted to a web design. You don't just paste an image into an HTML page and call it a website... it has to be cut-up and laid out with lots of thought and care. Knowing the rules, limitations, and constraints of web design will dramatically effect what you draw up in an image editor.

Before you draw anything, you will need to figure out some things first:

1) What resolution do you want to develop to?
2) What layout do you want to use?
3) Will your content be static, dynamic, or mixture of both?

The first thing to figure out is what desktop resolution you are going to develop to. Based on information from http://browsersize.com/, all web user desktops worldwide can be broken up into these percentages:

1024 x 768 - 56%
800 x 600 - 22%
1280 x 1024 - 13%
1152 x 864 - 3%
other - 6%

When actually drawing a website design up in an image editor, don't forget to subtract 30px from the width for your layouts. This is to accommodate the scrollbar that will appear to the right when content exceeds the screen height. Example: for a resolution of 800x600, your design should be 770px in width.

The main number you want to look at here is the width (the first number). Scrolling down is fairly well accepted as normal behavior for a website by all users. So the height is not as important as the width. Scrolling across is a different story. You will never want your design to have horizontal scrollbars at the bottom of the page. You will need to pay special attention to the width of your design when developing. If someone's desktop resolution is smaller than the resolution you designed to, they will have scrollbars at the bottom of their page and this will be deemed to be an unpleasant "viewing experience" for that user. The lower the resolution of your design, the more people that can be included in those that will have a nicer "viewing experience".

Before you just jump to the highest used resolutions (1024 x 768), consider your market. Who are you developing your website for? If your website is a forum about Java Web Development or CSS Web Design, then it's probably safe to figure that most of your users will be tech savvy. That means they will probably have nicer/newer computers, which means that you could probably develop to 1024 x 768 without worrying about to many people having a bad "viewing experience". On the other hand, if you are developing a website for a non-profit organization that provides free food and clothing to families with low incomes, you probably want to stick to 800x600. Your target audience probably can't afford the latest computers and may more than likely have older computers that were given away to them or purchased at a very cheap price. Another example is older people with bad eyesight - if your website draws in lots of senior citizens, they will probably want to see things at a lower resolution to make text and images larger.

You might also want to consider whether or not you want to ignore a quarter your market's "viewing experience". If your website is for a company that markets to the general public, I doubt their marketing department will like this. They will more than likely want something that looks appealing to everyone. This can be done easily by designing to 800x600 desktops. In fact, sometimes it's nice to have a background for your design. For those people who use higher resolutions, you can create more of an esthetically pleasing look to your design by having a background.

The second thing to figure out is what layout you want to use. A layout is how headers, footers, content, sidebars, etc. are placed on your page. Not every page has to have the same layout. For instance, you may want a unique layout just for your index (entry) page. That's fine, as long as most of the other pages on your site are consistent in their layout.

There are all sorts of layouts you can go with. There are those with menus on the side, menus on the top, some with sidebars and side boxes, and some without. There are those whose width stretch to fill your screen (liquid) and those whose width is a set size (static). Lots of possibilities here. A good place to look at some example layout can be found at the Layout Gala: http://blog.html.it/layoutgala/. This site provides the code for some of the most popular base layouts used in web design. All these layouts use valid markup and CSS, and have been tested successfully on Internet Explorer/win 5.0, 5.5, 6 and beta 2 preview of version 7; Opera 8.5, Firefox 1.5 and Safari 2. A great starting point for your web design. Again, keep in mind the two types of basic layouts: static and liquid. If you use a liquid layout, you will still need to determine the minimal width. It should be equal to the width of the resolution you have decided to design to. Your content should "float" appropriately as the browser is resized - either to the left, right, or center until they overflow, at which point they should float downward, pushing all your content down. Once you have reached your minimal width you have designed your site for, you are no longer accountable for your users "viewing experience". The content can overlap and run into each other... this now acceptable. You can try and force it to be static once it has reached its minimal width, at which point it will show horizontal scrollbars. This is sometimes deemed to be more pleasant than letting your content overlap itself. This is up to you.

Finally, you need to consider your content. Is it going to be fairly static? Will the content be updated by users frequently? Is there dynamic data that is used for content that comes from a database? Does the site use a content manager? The important thing here is to design to your content. In general, you should avoid designing static height pages... they should stretch appropriately to accommodate the data that is present on the page. This is one of the mistakes I see a lot of from graphic designers that don't know anything about the web. They code a watermark background that looks cool for a page of an exact height of, say, 600px because that was how big the page was with its content. But then a month later someone goes in adds some more content -now the website has an 800px height, and there is 200px at the bottom of the page that doesn't have a watermark and is even a completely different color/look than what was used for the first 600px. As a web designer you have to be aware of when to use "repeatable background images" or colors for backgrounds with dynamic data. Sometimes you can use static images or horizontal repeating images at the top or bottom, as long as they gracefully blend into the main background eventually.

This is also important for menus. Using a static image, like a tab, is fine as long as you are willing to go into an image editor and create a new tab every time you need to. However, you might consider using repeatable images/solid colors with text that automatically stretches when content is added. To do this is more complicated, but will save you time in the future. Plus, if you're using a content management system, this will be mandatory. You will have no idea how long someone might make their menu link, so you will need to be prepared for links that wrap and/or stretch dynamically. Again, solid colors or repeatable background can be used here. The doodlekit website buildertool is an example of when you would want to consider this. Advanced web designers that use this tool will need to consider these rules when developing. Some of the more complicated designs used by doodlekit have repeatable images/colors in the middle, and static images at the top and bottom, or on the left and right sides that blend into the middle.

Once you have figured out the resolution you want to design to, picked your layout, and determined how dynamic your content is, you are ready to finally start drawing! Keeping these in mind will determine how and what you design. When it comes time to convert it to an actual website, your web designer/developer will thank you!