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Dyslexia is a cognitive difficulty with the written form of language. It is characterised by difficulties in reading, writing, visual perception, sequencing and organisation and by limitations in working memory that affect dyslexics in different ways and in varying degrees of severity. The impact of such deficits can be exacerbated when dyslexics interact with hyperlinked structures and navigate web sites that are not designed optimally. Previous research has shown that despite increasing conformance to web accessibility standards, the web still suffers from deficiencies in support for navigation for the dyslexic user population. This thesis extends previous research in this area by means of empirical investigations and provides a rich insight into the navigational requirements of the dyslexic web user population. Several complementary studies were undertaken that investigate the effect of dyslexia on web interaction. First, a qualitative exploratory study was conducted to examine the problems that dyslexics experience on the web with a focus on navigation strategies and personalised approaches. Findings identified barriers that inhibit access to the web for dyslexics and revealed patterns in navigation strategies that relate to dyslexics’ profiles of key strengths and difficulties. Second, a quantitative exploratory eye tracking experiment was conducted to examine visual attention of dyslexics on web navigation structures. Eye movement analysis revealed marked differences in visual attention between dyslexics and non-dyslexic controls in web navigation. Two eye tracking experimental studies were conducted to test hyp~theses that were framed from the exploratory studies. The first experiment investigated dyslexic impairments that can cause functional difficulties in interacting with web navigation structures. Results showed that dyslexics took more time to complete tasks and experienced more disorientation on the web than non-dyslexic controls. Strong indications were found for web navigation problems being associated with limitations in working memory, difficulties in phonological processing and susceptibility to visual stress. The second experiment examined the stability of scanpaths in repeated exposure to web pages, which facilitates orientation and recognition in a visual scene. Significant variability of scanpaths was found between dyslexics and non-dyslexic controls in unconstrained viewing of text-heavy web pages. The eye tracking studies provided empirical evidence of the impact of dyslexia on web navigation difficulties by considering individual differences in the dyslexic user population. Beyond the experimental results, contributions of this work are providing an in-depth understanding of navigation problems experienced by dyslexics when interacting with the web and highlighting complexities involved in designing accessible interactive systems for individuals with dyslexia.