TECHNOLOGY FOCUS - CERAMICS AND GLASS - Preferred Components: The tempered glass comprises 50-75 (preferably 55-75) mol.% of silicon dioxide, 4-13 (preferably 4-12) mol.% of aluminum oxide, 0-1.5 (preferably 0-1) mol.% of boron oxide, 0-2 (preferably 0-1) mol.% of lithium oxide, 9-18 (preferably 11-16) mol.% of sodium oxide, 0-7 mol.% or 1-8 (preferably 2-7) mol.% of potassium oxide, 1.5-12 (preferably 3-12) mol.% of magnesium oxide, 0-3.5 (preferably 0-3) mol.% of calcium oxide, 0-3 (preferably 0-1) mol.% of strontium oxide, and 0-0.5 (preferably 0-0.1) mol.% of titanium dioxide, and 0.5-10%, 1-9% of zirconium oxide. In the tempered glass, a compression stress value of the compression stress layer is 300 MPa or more, and a thickness of the compression stress layer is greater than 10 mu m. The tempered glass has a liquidus temperature of 1075 degrees C or less. The tempered glass has a liquidus viscosity of 10(4.0) dPa-s or more. The tempered glass has a temperature at 10(4.0) dPa-s of 1250 degrees C or less. The tempered glass has a density of 2.6 g/cm3 or less. The tempered glass has a Young's modulus of 65 GPa or more. The tempered glass sheet has a surface formed by polishing by 0.5 mu m or more in a thickness direction. The tempered glass sheet has a Delta CS value of 50 MPa or less, the Delta CS value being a difference in compression stress value between compression stress layers in surfaces opposite to each other. The tempered glass sheet has a compression stress in a surface, where the tempered glass sheet has a length of greater than 500 mm, a width of 500 mm or more, a thickness of 0.5-1.5 mm, a Young's modulus of 65 GPa or more, a compression stress value of a compression stress layer of greater than 200 MPa, preferably greater than 400 MPa, a thickness of a compression stress layer of greater than 20 mu m, preferably greater than 30 mu m, than a degradation coefficient D of 0.01-0.6 or less than 0.6, preferably less than 0.4 and a Delta CS value of 50 MPa or less. The tempered glass sheet has a compression stress in a surface, where the tempered glass sheet comprises a molar ratio magnesium oxide/(magnesium oxide and calcium oxide) of greater than 0.5. Preferred Method: The tempered glass sheet is formed by a float method. EXAMPLE - Typical composition comprised (in mol.%): silicon dioxide (64.1); aluminum oxide (8.6); lithium oxide (0.2); sodium oxide (15.7); potassium oxide (3.6); magnesium oxide (3.3); calcium oxide (2.3); and zirconium oxide (2.2).