Recently, the use of portable terminals with touch screens such as smartphones has spread rapidly. Many users have used these devices to browse the internet or social networking services (SNS). There are many link texts (hyperlinked texts) to navigate between pages or to download files. However, interacting with link text in a portable terminal with a touch screen can often be difficult because link texts that have low text height and narrow space between lines (set by web designers who wanted to display as much information as possible on a screen of limited size) can cause accidental interactions. Many studies have evaluated usability when using portable terminals with touch screens and most of these studies have focused on Button, which is a basic GUI component. In contrast, GUI design approaches for link text have not been received sufficient attention. This study is aimed at evaluating the influence of two factors, namely the text height and the line spacing of link text, on the error rate and pointing time to overcome the usability problems associated with link texts. User experiments on pointing tasks were conducted for seven text heights (1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 mm) and five ratios of line spacing to text height (0.1, 0.3, 0.5, 0.7, and 1.0). The result shows that when the text height is 4.0 mm and the ratio of line spacing is 1.0 (the height of touchsensitive area is 8.0 mm), rapid and accurate pointing the link text can occur. We hope that these findings contribute to an easyto-use design for link texts.

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