Reading and writing in Japanese online is certainly a lot easier than it was just a few years ago, but there will still sometimes be a small amount of setting up required if using a western operating system.
There are three different characters within the Japanese language: Hiragana, Katakana and Kanji. Each Japanese character requires two bytes, and a special Japanese font set needs to be installed on your PC in order to display it. You'll also need to be using a Unicode font, such as Arial Unicode MS. While most Romanised text can be translated into Japanese with just a Japanese font set, there will be some elements of certain languages, for example characters with macrons, that will require a Unicode font.
The easiest way to ensure you're able to understand the Japanese language on the internet is to ensure you have the latest version of both your operating system and your web browser of choice. For example, with Hiragana characters, it's important to have the latest version of your internet browser and make sure you've got all the necessary updates for plug-in translators, otherwise Hiragana will appear in parentheses.
To work out whether your computer is able to read the Japanese language correctly, you can visit this webpage and check the correctly rendered Japanese characters against the way your computer is able to render them. If you notice strange symbols, such as blank boxes and question marks in the right-hand side of the column, then it's likely your computer does not support the display of Japanese symbols and you will need to install an appropriate plugin or change some of the settings on your computer. This can be done in the following ways:
If your computer uses a window operating system, it's fairly easy to change the settings to support the Japanese language. Simply go to your control panel, then type in 'regional and language options', then tick Japanese under the language tab. This is the method for computers using Windows Vista, 7 and 8.
For computers using a slightly older operating system, you'll have to install additional language files as these do not come automatically with the operating system as is the case with newer versions of Windows. To install language files, you'll need to go to 'regional and language options', then select 'additional language support' under the control tab. Japanese will be under either 'Japanese' or 'Far East languages', depending on your computer. To finish the installation you will most likely need the original Windows installation CD, and will then also need to configure your web browser accordingly.
If you have a Mac computer, it's likely you won't need to make any changes as with the OS X system Japanese is automatically recognised and displayed correctly. With OS 9, it's simply a case of going through the installation CD and selecting 'Customised Mac OS installation' then selecting software for the Japanese language under language kits.