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HTML Interview Questions Answers

Question 1 : Are there any problems with using frames?

Answer 1 : The fundamental problem with the design of frames is that framesets create states in the browser that are not addressable. Once any of the frames within a frameset changes from its default content, there is no longer a way to address the current state of the frameset. It is difficult to bookmark - and impossible to link or index - such a frameset state. It is impossible to reference such a frameset state in other media. When the sub-documents of such a frameset state are accessed directly, they appear without the context of the surrounding frameset. Basic browser functions (e.g., printing, moving forwards/backwards in the browser's history) behave differently with framesets. Also, browsers cannot identify which frame should have focus, which affects scrolling, searching, and the use of keyboard shortcuts in general. Furthermore, frames focus on layout rather than on information structure, and many authors of framed sites neglect to provide useful alternative content in the NOFRAMES element. Both of these factors cause accessibility problems for browsers that differ significantly from the author's expectations and for search engines.

Question 2 : Are there any problems with using tables for layout?

Answer 2 : On current browsers, the entire table must be downloaded and the dimensions of everything in the table must to be known before the table can be rendered. That can delay the rendering of your content, especially if your table contains images without HEIGHT or WIDTH attributes. If any of your table's content is too wide for the available display area, then the table stretches to accomodate the oversized content. The rest of the content then adjusts to fit the oversized table rather than fitting the available display area. This can force your readers to scroll horizontally to read your content, or can cause printed versions to be cropped. For readers whose displays are narrower than the author anticipated, fixed-width tables cause the same problems as other oversized tables. For readers whose displays are wider than the author anticipated, fixed-width tables cause extremely wide margins, wasting much of the display area. For readers who need larger fonts, fixed-width tables can cause the content to be displayed in short choppy lines of only a few words each. Many browsers are especially sensitive to invalid syntax when tables are involved. Correct syntax is especially critical. Even with correct syntax, nested tables may not display correctly in older versions of Netscape Navigator. Some browsers ignore tables, or can be configured to ignore tables. These browsers will ignore any layout you've created with tables. Also, search engines ignore tables. Some search engines use the text at the beginning of a document to summarize it when it appears in search results, and some index only the first n bytes of a document. When tables are used for layout, the beginning of a document often contains many navigation links that appear before than actual content. Many versions of Navigator have problems linking to named anchors when they are inside a table that uses the ALIGN attribute. These browsers seem to associate the named anchor with the top of the table, rather than with the content of the anchor. You can avoid this problem by not using the ALIGN attribute on your tables. If you use tables for layout, you can still minimize the related problems with careful markup. Avoid placing wide images, PRE elements with long lines, long URLs, or other wide content inside tables. Rather than a single full-page layout table, use several independent tables. For example, you could use a table to lay out a navigati

Question 3 : Can I have two or more actions in the same form?

Answer 3 : No. A form must have exactly one action. However, the server-side (e.g., CGI) program that processes your form submissions can perform any number of tasks (e.g., updating a database, sending email, logging a transaction) in response to a single form submission.

Question 4 : Can I have two or more Submit buttons in the same form?

Answer 4 : Yes. This is part of HTML 2.0 Forms support (some early browsers did not support it, but browser coverage is now excellent). The submit buttons must have a NAME attribute. The optional VALUE attribute can be used to specify different text for the different submit buttons. To determine which submit button was used, you need to use different values for the NAME and/or VALUE attributes. Browsers will send to the server the name=value pair of the submit button that was used. Here is an example: <input type="submit" name="join" value="I want to join now"> <input type="submit" name="info" value="Please send full details"> Note that if you are using image submit buttons, you need to provide different NAME attributes for them too. Also, browser behavior can be inconsistent when the form is submitted without a submit button (e.g., by hitting ENTER). If you're unsure what results you're going to get when you submit your form, TipJar has a standard script which you can use. Code this, for example (assuming method "post"): <form method="post" action="http://www.yoursite.com/cgi-bin/test"> and then go through the motions of submitting your form. The TipJar server decodes the form input, and displays the result to you.

Question 5 : Can I nest tables within tables?

Answer 5 : Yes, a table can be embedded inside a cell in another table. Here's a simple example: <table> <tr> <td>this is the first cell of the outer table</td> <td>this is the second cell of the outer table, with the inner table embedded in it <table> <tr> <td>this is the first cell of the inner table</td> <td>this is the second cell of the inner table</td> </tr> </table> </td> </tr> </table> The main caveat about nested tables is that older versions of Netscape Navigator have problems with them if you don't explicitly close your TR, TD, and TH elements. To avoid problems, include every </tr>, </td>, and </th> tag, even though the HTML specifications don't require them. Also, older versions of Netscape Navigator have problems with tables that are nested extremely deeply (e.g., tables nested ten deep). To avoid problems, avoid nesting tables more than a few deep. You may be able to use the ROWSPAN and COLSPAN attributes to minimize table nesting. Finally, be especially sure to validate your markup whenever you use nested tables.  

Question 6 : Can I prevent a form from being submitted again?

Answer 6 : No. The server-side (e.g., CGI) program that processes the form submission must handle duplicate submissions gracefully. You could generate the form with a server-side (e.g., CGI) program that adds a hidden field with a unique session ID. Then the server-side program that processes the form submission can check the session ID against a list of previously used session IDs. If the session ID has already been used, then an appropriate action can be taken (e.g., reject the submission, or update the previously submitted data). Ultimately, your server-side program must be smart enough to handle resubmitted data. But you can avoid getting resubmitted data by not expiring the confirmation page from form submissions. Since you want to expire pages quickly when they have transient data, you might want to avoid putting transient data on the confirmation page. You could provide a link to a database query that returns transient data though.

Question 7 : Can I use percentage values for <TD WIDTH=...>?

Answer 7 : The HTML 3.2 and HTML 4.0 specifications allow only integer values (representing a number of pixels) for the WIDTH attribute of the TD element. However, the HTML 4.0 DTD allows percentage (and other non-integer) values, so an HTML validator will not complain about <TD WIDTH="xx%">. It should be noted that Netscape and Microsoft's browsers interpret percentage values for <TD WIDTH=...> differently. However, their interpretations (and those of other table-aware browsers) happen to match when combined with <TABLE WIDTH="100%">. In such situations, percentage values can be used relatively safely, even though they are prohibited by the public specifications.

Question 8 : Do I have to memorize a bunch of tags?

Answer 8 : No. Most programs that help you write HTML code already know most tags, and create them when you press a button. But you should understand what a tag is, and how it works. That way you can correct errors in your page more easily.

Question 9 : Do search engines dislike frames?

Answer 9 : Search engines can link directly to framed content documents, but they cannot link to the combinations of frames for which those content documents were designed. This is the result of a fundamental flaw in the design of frames. Search engines try to provide their users with links to useful documents. Many framed content documents are difficult to use when accessed directly (outside their intended frameset), so there is little benefit if search engines offer links to them. Therefore, many search engines ignore frames completely and go about indexing more useful (non-framed) documents. Search engines will index your <NOFRAMES> content, and any content that is accessible via your  

Question 10 : How can I allow file uploads to my web site?

Answer 10 : These things are necessary for Web-based uploads: * An HTTP server that accepts uploads. * Access to the /cgi-bin/ to put the receiving script. Prewritten CGI file-upload scripts are available. * A form implemented something like this: <form method="post" enctype="multipart/form-data" action="fup.cgi"> File to upload: <input type=file name=upfile><br> Notes about the file: <input type=text name=note><br> <input type=submit value=Press> to upload the file! </form> Not all browsers support form-based file upload, so try to give alternatives where possible. The Perl CGI.pm module supports file upload. The most recent versions of the cgi-lib.pl library also support file upload. Also, if you need to do file upload in conjunction with form-to-email, the Perl package MIME::Lite handles email attachments.

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