The focal point for Western culture is the center of the page followed by the upper left. This varies for other cultures depending upon whether they read horizontally or vertically, and left to right or right to left. Technical resources Web sites created for an audience of users with T-1 lines can put a greater burden on memory and bandwidth loads than websites that one hopes will be accessed worldwide. Consider the likelihood of your audience having plug-ins, recent versions of browsers, etc. Readability Monitors vary in resolution, brightness, and flicker.
Browsers vary in presentation of colors, indentions, frames.
All these vagaries combined can make the web site that is presented look very different from the web site that was created. And they can conspire to make reading online a nightmare. Thus, web designers have to work hard to lay out information carefully to make it as easy to read as possible. Chunk information using tables, lists, frames, and white space. Choose fonts and colors with readabiltiy in mind.