When using IE7, the Toolbar in the Wiki Markup Editor will overlap the first line of text, making it invisible. The workaround is to switch to Preview or Rich Text and then back to Wiki Markup, and then you will see the first line.

Steps To Reproduce in IE7
1) Set Wiki Markup as the preferred editing mode
2) Edit a page
Expected Result: The first line of text in the page is visible below the editing toolbar
Actual Result: the first line of text is obscured by the editing toolbar.

The attached image shows a page whose first line, "This is the first line of text.", is obscured by the toolbar so that only the second line, "This is the second line of text" can be viewed.