The purpose of this study was (a) to evaluate ten online periodic table sources for their accuracy and (b) to compare the types of information and links provided to users. Limited studies have been reported on online periodic table (Diener and Moore 2011; Slocum and Moore in "J Chem Educ" 86(10):1167, 2009). Chemistry students' understanding of periodic table is vital for their success in chemistry, and the online periodic table has the potential to advance learners' understanding of chemical elements and fundamental chemistry concepts (Brito et al. in "J Res Sci Teach" 42(1):84-111, 2005). The ten sites were compared for accuracy of data with the "Handbook of Chemistry and Physics" (HCP, Haynes in "CRC Handbook of Chemistry and Physics: A Ready-Reference" book of chemical and physical data. CRC Press, Boca Raton 2012). The 10 sites are the most visited periodic table Web sites available. Four different elements, carbon, gold, argon, and plutonium, were selected for comparison, and 11 different attributes for each element were identified for evaluating accuracy. A wide variation of accuracy was found among the 10 periodic table sources. Chemicool was the most accurate information provider with 66.67% accuracy when compared to the HCP. The 22 types of information including meaning of name and use in industry and society provided by these sites were, also, compared. "WebElements," "Chemicool," "Periodic Table Live," and "the Photographic Periodic Table of the Elements" were the most information providers, providing 86.36% of information among the 10 Web sites. "WebElements" provides the most links among the 10 Web sites. It was concluded that if an individual teacher or student desires only raw physical data from element, the Internet might not be the best choice.