Many evaluation systems were developed for evaluating accessibility of websites, however, they produce various results. Meanwhile the current state of web accessibility evaluation systems is promising, yet not sufficient. Moreover it is difficult to detect for sure if they are correctly applying accessibility guidelines. We created an analytical study of the available web accessibility guideline and the available web accessibility tools. AChecker is a well-known existing tool that evaluates web page compliance with WCAG 2.0 and shows its implemented guidelines. We enhanced the functionalities of this tool by detecting its problems and adding a repair tool. The deficiencies of AChecker are of three types that are unclear comments, redundancy of errors reporting or lack of automatic or semi-automatic repair. A new interactive evaluation tool (IWAET) is developed based on AChecker. The design and implementation of the system were described. Usability evaluation study for the proposed system were conducted. The study involved a group of web developers with different levels of programming experience and no accessibility knowledge. Both a quantitative and qualitative approaches were adopted in usability evaluation study. Moreover, in this study the usability of the proposed system is compared to AChecker based on the satisfaction, effectiveness and efficiency usability measures. The results of the usability evaluation of the proposed system showed the effectiveness and efficiency of the system as well as its ability to solve the problems identified in the AChecker accessibility evaluation tool.